Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/22—Processes or apparatus for obtaining an optical image from holograms
  • G03H1/2202—Reconstruction geometries or arrangements
  • G03H1/2205—Reconstruction geometries or arrangements using downstream optical component
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/22—Processes or apparatus for obtaining an optical image from holograms
  • G03H1/2294—Addressing the hologram to an active spatial light modulator
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/22—Processes or apparatus for obtaining an optical image from holograms
  • G03H1/2202—Reconstruction geometries or arrangements
  • G03H1/2205—Reconstruction geometries or arrangements using downstream optical component
  • G03H2001/2207—Spatial filter, e.g. for suppressing higher diffraction orders
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/22—Processes or apparatus for obtaining an optical image from holograms
  • G03H1/2202—Reconstruction geometries or arrangements
  • G03H1/2205—Reconstruction geometries or arrangements using downstream optical component
  • G03H2001/221—Element having optical power, e.g. field lens
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2222/00—Light sources or light beam properties
  • G03H2222/34—Multiple light sources
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2223/00—Optical components
  • G03H2223/12—Amplitude mask, e.g. diaphragm, Louver filter
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2223/00—Optical components
  • G03H2223/19—Microoptic array, e.g. lens array
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2225/00—Active addressable light modulator
  • G03H2225/30—Modulation
  • G03H2225/33—Complex modulation
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2225/00—Active addressable light modulator
  • G03H2225/55—Having optical element registered to each pixel
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2226/00—Electro-optic or electronic components relating to digital holography
  • G03H2226/05—Means for tracking the observer

Definitions

• the invention relates to a device for generating holographic reconstructions with light modulators, to which
• At least one pixelated light modulator illuminated by at least one light source at least one pixelated light modulator illuminated by at least one light source
• a focusing optical element array whose optical elements are each associated with a group of codable pixels of the light modulator and which the light sources in an image plane after the light modulator as
• a control unit which is in communication with the light modulator and in which the holographic coding of the pixelized Kodier products the light modulator is calculated by means of programmable means include.
• a pixelated light modulator is not necessarily understood to mean a modulator consisting of an arrangement of discretely controllable elements. It can also be a modulator with a continuous coding surface, which is formally divided into discrete elements by the information to be displayed.
• optical elements are not necessarily understood to mean only conventional glass lenses, but in a broader sense may also be refractive or diffractive optical elements that perform the same function.
• a reconstruction of a three-dimensional scene arises in a reconstruction space when the light modulator is illuminated with sufficiently coherent light. It arises but also unwanted periodic repetitions in the form of higher diffraction orders due to the discrete representation of the hologram in the light modulator. Depending on the coding of the hologram used, but also within a diffraction order, undesired regions may occur which must be filtered out.
• One conventional method of eliminating spurious diffraction orders is the use of a filter unit, for example a 4f array, with which such diffraction orders can be filtered out.
• the filter unit can be dimensioned so that it passes areas that are less than or equal to a diffraction order.
• a holographic projection apparatus and a method for generating holographic reconstructions of scenes for one and two-dimensional encodable üchtmodulatoren are described, the light source, an optically focusing system, the respective associated light modulator, a projection system and between the light modulator and the projection system arranged filter aperture, which is located in the image plane of the light source image contains.
• the optically focusing system is an illumination optic for the light modulator and an imaging optic for the light source, which images the light source into the image plane of the illumination optics, the Fourier transform of the light modulator also being produced in the image of the light source.
• a control unit is provided, which is provided not only for the dynamic coding of the light modulator, but also for the tracking of the visibility range and thus also the holographic reconstruction according to the observer position.
• a position detection system is present, which is connected to the control unit.
• the coding of the light modulator is changed, wherein depending on the position of the viewer, the reconstruction of the three-dimensional scene in the horizontal, vertical and / or axial position horizontally and / or vertically shifted and / or rotated at an angle visible.
• the direct view device with the twenty-inch display may include the light source, an optically focusing system, the respective associated light modulator, a projection system, and a filter shutter located between the light modulator and the projection system located in the image plane of the light source image.
• the filter diaphragm has an aperture which only transmits the intended diffraction order of the Fourier transform of the light modulator.
• the projection system images the aperture into another plane, which is also the observer plane. From the observer plane, in a visibility range corresponding to a diffraction order of the Fourier spectrum, the observer can see the holographic reconstruction.
• the associated filter unit requires in addition to the filter panel at least two lenses, at least one of which is about as large as the Lichtmoduiator itself, which represents the display. This means, for example, in the case of the holographically encoded twenty-inch display, a large lens of at least forty centimeters in diameter.
• lenses usually have a usable imaging quality only for a specific focal length to aperture ratio of significantly greater than one and the filtering takes place at the location of the image of the light source, in this case in the focal plane of the first lens, in this example a filter unit - first large lens, filter aperture, second large lens - needed, which has a depth extent of the order much larger than forty centimeters in front of the light modulator.
• a filter unit - first large lens, filter aperture, second large lens - needed which has a depth extent of the order much larger than forty centimeters in front of the light modulator.
• Another problem is that there are very small usable diffraction angles in display holography due to the currently usable pixel dimensions of typical light modulators, which in turn cause a small viewing window.
• a method of display holography described in the publication US Pat. No. 3,633,989 provides that HPO holograms (horizontal parallex only holograms) are used in which hologram coding takes place in only one dimension.
• HPO holograms horizontal parallex only holograms
• normally calculated values for the one-dimensional hologram are written into each line of a light modulator independently of one another.
• a gain for the diffraction angle can then be achieved by encoding hologram values, which are usually encoded in a plurality of adjacent pixels, in this case in sub-pixels of several lines.
• the invention has for its object to provide a device for generating holographic reconstructions with light modulators, which is designed so that on the one hand a costly arrangement of at least the optical system avoided and the other part of the usable for the visibility range diffraction angle can be increased. It should be the Dimensions of the device in the axial direction are kept as low as possible.
• a focusing optical element field arrangement whose optical elements are each assigned to a group of codable pixels of the light modulator and which image the light sources in an image plane downstream of the light modulator as light source images, and
• the light modulator is provided with a filter aperture array provided with a plurality of apertures, which is located in the region of the image plane of the light source images and whose apertures are formed within the filter aperture array such that the apertures each pass a predetermined range of magnitude less than or equal to a diffraction order of the Fourier transform from the diffraction spectrum resulting from the holographic encoding of the light modulator.
• a light source with a beam expansion optics can be arranged in front of the light modulator.
• a dynamic shutter modulator can be provided between the beam expansion optics and the focusing optics element array.
• a light source array arranged in front of the light modulator can be arranged with a multiplicity of light sources.
• the device may have a light source field arrangement, a first optics element array arrangement as a beam expansion optics and a second optics element array arrangement with a plurality of spherical optical elements, for example in the form of spherical lenses as a screen for the viewer.
• the light source or the first light source array is associated with a power supply device.
• the light modulator coding control unit is part of a control system that includes a light source array control unit and / or a filter aperture array control unit and a current location location of the viewer.
• the position detection unit can be connected to the two units at least by signal technology.
• the two units may be in communication with a shifting device which shifts the formed light sources of the light source array and / or the filter diaphragms of the filter diaphragm array as movable components depending on signals from the position detection unit in their respective plane.
• a shifting device which shifts the formed light sources of the light source array and / or the filter diaphragms of the filter diaphragm array as movable components depending on signals from the position detection unit in their respective plane.
• the first and the second optical element array it is also possible for the first and the second optical element array to be designed to be displaceable.
• the light source or filter diaphragm field arrangements can be designed both as static and as dynamic, adjustable by the control system optical components.
• the pixelated coding surface of the light modulator can have, for example, square-shaped pixels.
• the first optical element field arrangement represents an illumination optical system for the light modulator and an imaging optical system for the light source field array, which images the light source array into the Fourier plane of the light modulator where the images of the light source field arrangement coincide with the Fourier transforms of the irradiated pixels of the respective subarea of the light modulator, and wherein the filter array array passing the predetermined diffraction order is placed in the region of the focal plane.
• the filter aperture array may comprise a grid of apertures each passing only the predetermined diffraction order of the Fourier transform or portions thereof.
• the projecting second optical element field arrangement with the in particular two-dimensionally formed, spherical lenses forms the apertures of the filter aperture array in a second plane, which is also the observer plane, from.
• the mutual arrangement of the optical elements and the filter diaphragms is chosen so that the images of all apertures in the observer plane coincide and form a viewer window.
• the first optical element array may be a two-dimensional array of spherical lenses arranged after the point light sources of the light source array.
• a single spherical lens of the first optical element array and a single spherical lens of the second optical element array may have a dimension in the range of typically about three to ten millimeters.
• the size of the pinholes of the filter aperture array is dependent on the pixel pitch p of the light modulator and the focal length of the lenses of the first optical element array.
• the filter aperture field arrangement can be designed as a S hutter modulator whose controllable openings are in the range of the dimensions of one or more pixels of the shutter modulator.
• the program-technical means for coding the pixels of the light modulator in the control unit can be adapted to the structure of the device according to the invention.
• the coding of the hologram values can take place in a plurality of horizontally or vertically adjacent pixels of one or more lines of the light modulator.
• control system in particular in the associated control unit, it is possible to perform a holographic coding in only one dimension, wherein the values inscribed in a group of rows or columns of the light modulator are related to one another.
• the first optical element array may represent a lenticular field array with cylindrical lenses illuminated by line light sources and associated with a slotted aperture filter diaphragm array.
• a sufficiently coherent illumination of the light modulator then only has to be carried out in the range of the group of a few lines.
• a dynamic shutter modulator to shift the position of the aperture.
• the light source field arrangement can consist of a sequentially switchable arrangement of adjacent light sources, which in a certain time interval a particular vertical range can be illuminated, which is adjustable by the control system.
• diverging lenses can be used, wherein the entirety of the diverging lenses can likewise be in the form of a diverging lens field arrangement and can be arranged directly downstream of the filter aperture field arrangement.
• one-dimensional, slot-shaped or two-dimensional hole-like filter diaphragm field arrangements can be used.
• the filter aperture field arrangement can be designed statically in the form of a shadow mask.
• a dynamic filter diaphragm field arrangement can be provided via the signal-controlled displacement devices of the control system.
• the filter aperture array can be a fast switching amplitude light modulator in which the variation of the transmission of individual pixels causes filtering, wherein the switched pixels, which then act as pinhole, approximately correspond to the size of the opening of the pinhole diaphragm of the static filter diaphragm array.
• the light source array may, in concert with the dynamic filter aperture array, be a fast switching amplitude light modulator illuminated by a light source as a whole and in which the variation of the transmission of individual pixels causes a light beam transmission, the pixels then serving as beam aperture act, about the size of the diameter of the light sources of the static light source array have.
• FIG. 1 is a schematic representation of the side view or top view of a device according to the invention for generating holographic reconstructions
• 2 a section of the coding surface of a two-dimensionally codable pixelized light modulator with square pixels
• FIG. 1 is a schematic representation of the side view or top view of a device according to the invention for generating holographic reconstructions
• 2 a section of the coding surface of a two-dimensionally codable pixelized light modulator with square pixels
• Fig. 3 is a schematic representation of the side view of a variant of the device according to the invention for generating holographic
• FIG. 3a shows the arrangement of components essential to the invention
• 3b show a section of the coding surface of a one-dimensional codable pixelated light modulator
• FIGS. 1 and 3 a shows a schematic representation of the side view of a device according to the invention for generating holographic reconstructions with an adjustable filter diaphragm field arrangement and an adjustable light source field arrangement according to FIGS. 1 and 3 a and
• Fig. 5 is a schematic representation of the side view of a device according to the invention for generating holographic reconstructions of Fig. 3a with a diverging lens array arrangement.
• FIG. 6 shows a schematic structure of part of a 4f arrangement of the device according to the invention
• FIG. 7 shows the phase representation of the phases of the two pixels of the macropixel on the phase unit circle according to FIG. 6, FIG.
• FIG. 8 shows two amplitude-phase-position diagrams for a macropixel of two pixels according to FIGS. 6 and 7, wherein FIG
• Fig. 8a shows the amplitude dependence on the position before filtering
• Fig. 8b show the amplitude as a function of the position after filtering by the lenticular array.
• 1 shows a schematic representation of a device 1 according to the invention for the holographic reconstruction of a three-dimensional scene 9 with a light modulator 2, which has a housing 3 in which at least
• a light source array 4 having a plurality of light sources 41, at least one pixelated light modulator 2, which is the light source
• Field arrangement 4 is arranged downstream,
• the lenses 51 are each assigned to a group of codable pixels 21 of the light modulator 2 and the individual light sources 41 of the light sequencer array 4 in an image plane 6 after the light modulator 2 as light source images
• a control unit 7 which is in communication with the light modulator 2 and in which the holographic coding of the pixelized Kodier Chemistry 22 of the Lichtmoduiators 2 is calculated by program means are located.
• the light modulator 2 is associated with a filter aperture field arrangement 8 provided with a multiplicity of apertures in the form of apertured apertures 81, which is located in the region of the image plane 6 of the light source images 42 and whose apertured apertures 81 are formed within the filter aperture field arrangement 8 in such a way Perforated apertures 81 in each case pass a predetermined diffraction order or parts thereof out of the diffraction spectrum produced by the holographic coding of the light modulator 2.
• a light source 11 with a beam expansion optics 12 and a second lens field arrangement 13 with a plurality of spherical lenses 131 can be present as screen for the viewer 14.
• the light source 11 or independent of the light source 11 of the first light source array 4 is associated with a power supply device 15.
• the control unit 7 for coding the light modulator 2 may be part of a control system 16, to which, according to FIG. 1, a unit 17 for controlling the light source array 4 and a unit 18 for controlling the filter diaphragm Field arrangement 8 and a position detection unit 19 may include the location of the viewer 14.
• the position detection unit 19 is connected to the two units 17 and 18 at least by signal technology.
• the two units 17 and 18 are connected to a displacement device 20, which is the movable components such as the light sources 41 of the light source array 4 and / or the filter aperture 81 of the filter aperture array 8 or the lenses 51 of the lens array 5 depending shifts to signals from the position detection unit 19 in its respective plane.
• a displacement device 20 is the movable components such as the light sources 41 of the light source array 4 and / or the filter aperture 81 of the filter aperture array 8 or the lenses 51 of the lens array 5 depending shifts to signals from the position detection unit 19 in its respective plane.
• FIG. 1 thus shows a filtering on a holographically coded light modulator 2, which is formed as part of the device 1 according to the invention and in which the light source array 4 in combination with the first lens array 5, the filter aperture array 8 and the second Lens array 13 are used.
• FIG. 2 schematically shows the pixelated coding surface 22 of the light modulator 2, wherein the pixels 21 of square design here extend in the xy direction of the xyz coordinate system 10 indicated in FIG.
• p is the center distance of two adjacent pixels 21
• the coordinate z is the axial direction of extension of the device 1, associated optical components.
• the first optical element array 5 represents an illumination optical system for the light modulator 2 and an imaging optical system for the light source array 4, which images the light source array 4 into the focal plane 6 given as a Fourier plane of the light modulator, the images of the light sources Field arrangement 4 coincide with the Fourier transform of the irradiated pixels of the respective subregion of the light modulator 2 and wherein the predetermined diffraction order passing filter aperture array 8 is placed in the region of the focal plane.
• the filter diaphragm field arrangement 8 has a grid of apertures in the form of pinhole apertures 81, which in each case transmits only the intended diffraction order of the Fourier transform or parts thereof.
• the projecting second lens array 13 having the two-dimensionally arranged spherical ones Lenses 131 form the pinhole apertures 81 into a second plane 61, which is also the observer plane, with the images of the individual apertured apertures 81 superimposed in a visibility region. From the observer plane 61, in the visibility region corresponding to a diffraction order of the Fourier spectrum, by a viewer 14, the holographic reconstruction 9 of the three-dimensional scene can be seen.
• the first optics element Feidan extract 5 may be a two-dimensional arrangement with spherical lenses 51, which are arranged after the point light sources 41 of the light source array 4, wherein a two-dimensional filter aperture array 8 of pinhole apertures 81 and a second optical element array 13 is provided.
• the device 1 represents in FIG. 1 a section through the rows or columns of the field arrangements 4, 5, 6, 13.
• a single lens 51 of the first optical element array 5 and a single lens 131 of the second optical element array 13 may have a dimension in the range of typically three to ten millimeters.
• the depth of the structure of the device 1 in the z-direction only increases to a moderate extent by the filtering with the field arrangements 4, 5, 6, 13 and remains well below the dimensions of the structure with the large lenses described in the prior art.
• the filter aperture field arrangement 8 is a two-dimensional grid with small apertures - the apertured apertures 81 -.
• the size of the apertures 81 depends on the pixel pitch p of the light modulator 2 shown in FIG. 2 and the focal length of the lenses 51 of the first optical field array 5, which determine the extent of a diffraction order in the Fourier plane.
• a predetermined value may be in the range of 0.1 mm to 0.2 mm.
• the filter diaphragm field arrangement 8 can also be designed as a shutter modifier with controllable openings whose dimensions are in the range of the dimensions of one or more pixels of the shutter modulator.
• control unit 7, program center! for the holographic coding of the pixels 21 of the light modulator 2 can be matched to the structure of the device 1.
• FIG. 3a is a schematic representation of the device 1 according to the invention for the production of holographic reconstructions 91 in a disarmed form compared to Fig. 1, which consists of a light source array 43, a first optical element field array 5, a light modulator 23 and a The light modulator 23 downstream Fiiterblenden array 8, which is located in the image plane 6 of the light source images 42 consists.
• HPO horizontal parallax only holograms
• holograms are used conventionally in display holography, in which hologram coding is performed in only one dimension, e.g. in the y-direction, as shown in Fig. 3, 3b, takes place.
• values of amplitude and phase calculated independently of one another are normally written into each row of the light modulator 23.
• one-dimensional holographic codes 24, 25, 26, 27 within the light modulator 23 only one-dimensional holographic reconstruction can take place. The e.g. Accordingly, the light wave diffracted at the one-dimensional HPO hologram of the light modulator 23 expands only in the horizontal direction in the visibility region of the plane 61.
• the first optical element field arrangement 5 and / or second optical element field arrangement 13 in FIG. 1 may be a cylindrical lens lenticular field arrangement illuminated by line-shaped light sources 41 and associated with a filter aperture array 8 with slotted apertures 82 ,
• FIG. 1 shows a top view of the device 1.
• VPO (vertical parallax only) holograms are also conceivable in which everything is rotated by 90 degrees.
• One possibility of the calculation in the control unit 7 for this purpose is, for example, a representation of a complex number by a plurality of phase values, wherein the calculation of a one-dimensional arrangement of complex hologram values in the horizontal direction, in the y-direction, the arrangement of the phase values to a respective complex number but in vertical superimposed pixels takes place.
• a coherent illumination only in each case of the group 28 of a few lines 24, 25, 26, 27 is necessary. If, however, a group 28 of lines 24, 25, 26, 27 of a light modulator 23 is coherently illuminated, a path difference between the individual lines that varies in the vertical direction, in the x direction, arises, which leads to deviations from the expected reconstruction ,
• the desired signal is transmitted in the image plane 6 as a coherent addition of a plurality of light modulator lines 24, 25, 26, 27 itself-not its Fourier transforms-or unwanted portions thereof are filtered out.
• a viewer 14 in the visibility range of the plane 61 also move vertically and the viewer 14 can see the original reconstruction 91 and the reconstruction 92 displaced therefrom from different vertical positions.
• light must come from the image plane 6 in the corresponding vertical position.
• a diverging lens array 53 is provided adjacent to the image plane 6, which widens the angle at which the light propagates in the vertical direction.
• a favorable alternative to setting the visibility area in the plane 61 to the observer 14 may be a dynamic shutter for shifting the position of the apertures 81 or 82 in the filter aperture array
• Phase encoding each for a complete line a particular phase offset can be added - or with a movable light source array 4. This has the advantage that even a relatively slow switching
• Light modulator 2 can be used.
• the latter can also, as shown for example in FIG. 4, be a light source field arrangement 4 in which adjacent light sources 41 are switched on one after the other under the control of the unit 17 for controlling the light source field arrangement 43.
• a certain vertical area, occupied by the directional symbol L can be scanned.
• Fig. 4 also shows a possible shift, with the directional sign F occupies, the apertures 82 of the filter aperture array 8 in the image plane 6, wherein the filter aperture array 8 may also be formed as a dynamic light modulator.
• Fig. 5 shows the said possibility of using additional diverging lenses 52 for increasing the visibility range usable by the viewer 14 in the plane 61, wherein the entirety of the mutually parallel diverging lenses 52 formed in the form of a diverging lens array 53 and the filter aperture array 8 immediately downstream can be.
• the device 1 makes it possible to filter unwanted diffraction orders in combination with a light source field arrangement 4 for each individual area of a hologram illuminated sufficiently coherently by a light source 41.
• This allows in particular the use of small compact filter units, which can also be mounted in front of a large holographic screen 13.
• the use of one-dimensionally directed - preferably slot-shaped - or two-dimensional - preferably hole-like - filter diaphragm field arrangements 8 may be possible.
• the filter aperture array 8 may be formed statically in the form of a shadow mask.
• Another embodiment of the device 1, which allows tracking or a regular scanning of a specific visibility region of the plane 61 for the viewer 14, is the dynamic execution of the filter aperture array 8 via the signal-controllable displacement devices 20 of the control system 16.
• the filter aperture array 8 may be, for example, a fast switching amplitude light modulator, in which the variation of the transmission of individual Pixel or pixel groups causes a filter.
• the pixels or pixel groups which can then act as apertures in the form of pinhole apertures, then have approximately the size of the opening of the pinhole apertures 81. Since the individual filter units of the filter aperture field arrangement 8 are illuminated with light sources which are incoherent relative to one another, Field arrangement 8 no new diffraction structure.
• the light source array 4, in coordination with the filter aperture array 8, can be a fast switching amplitude light modulator in which the variation of the transmission of individual pixels or groups of pixels causes a light transmission, the pixels or groups of pixels, which then act as a light transmission opening, approximately the size of the diameter of the light sources 41 of the static light source array have.
• An advantageous application of the filter array described is to filter out an unwanted angle-dependent phase difference that is unavoidable when encoding complex hologram values in several adjacent pure phase pixels.
• This unwanted phase difference arises in addition to the programmed-in desired phase difference in that the pixels belonging to a hologram value are arranged next to one another and not behind one another.
• the optical element field arrangements 5 and 13 together with the filter aperture array 8 are interpreted as a 4f filter arrangement and a complex hologram value is coded by pure phase values in 2 adjacent pixels.
• FIG. 6 shows in a longitudinal section a part of a 4f arrangement 31 with a light modulator 2, a first focusing optical element array 5 arranged downstream in this example, and a downstream second focusing optical element array 13, according to which as output 30 the filtered pixel information of the light modulator 2 is present, wherein the filter diaphragm field arrangement 8 with the apertures 81 is located between the two optical element field arrangements 5 and 13.
• the first optical element array 5 has lenses focussing as optical elements 51
• the second optical element array 13 also has focussing lenses as optical elements 131, wherein both optical element array arrangements can be designed as lenticular field arrangements.
• two pixels 291, 292 each are provided as a group or macro-pixel 29, wherein the macro-pixel 29 has the size of the lenses 51.
• the size of the lenses 51 is shown in FIG. 6 as an example with 60 .mu.m, the apertures 81 have a size of 10 .mu.m and the distances between the light modulator 2 and the filter aperture array 8 or the output 30 and the filter aperture array 8 amount each 1 mm. In particular, the dimensions are therefore given to indicate a relationship to the size ratios of the prior art direct view device.
• Fig. 7 shows the coding of a complex hologram value by 2 pure phase values on the phase unit circle 293 with the axes Im (imaginary part) and Re (real part), the phase 2911 of the pixel 291 and the phase 2921 of the pixel 292 of the light modulator 2 according to a Parallelogram 295 are added to a resulting complex value 294 of the macropixel 29 having the desired of 1 different amplitude and the desired phase.
• Fig. 8 shows the coding of a complex hologram value by 2 pure phase values on the phase unit circle 293 with the axes Im (imaginary part) and Re (real part), the phase 2911 of the pixel 291 and the phase 2921 of the pixel 292 of the light modulator 2 according to a Parallelogram 295 are added to a resulting complex value 294 of the macropixel 29 having the desired of 1 different amplitude and the desired phase.
• Fig. 8 shows the coding of a complex hologram value by 2 pure phase values on the phase unit circle 293 with the
• Pixels 291 and 1 exp -0,17i of the pixel 292 generated.
• Phase pixels are equal and have the value "1"
• the pixel phase 2911 of the pixel 291 is 2.17rad
• the pixel phase 2921 of the pixel 292 is -0.17rad.
• an oblique illumination would still result in an additional phase difference between the two pixels that depends on the illumination angle, because they are next to one another lie. This would corrupt the desired complex value, but is filtered out by the 4f filtering for each pixel group, so that the macropixet 32 at the output of the 4f system actually has the desired phase and amplitude value.
• FIG. 8b shows the comparison between practical filtering in the 4f array 31 and calculated filtering before and after the filtering in the image plane 6, the values before the filtering being the coding of the pixels 291, 292 in the light modulator 2 and the values after the Filtering at the output 30 immediately after the optical element filter assembly 13, which may be a lenticular array, are represented by the position to coordinate largely parallel drawn lines with respect to the amplitude and phases.
• the small deviations in FIG. 8b, both in the resulting amplitude distribution and in the resulting phase distribution between the filtered macropixel 29 and the ideal complex-valued macropixel 32, are largely negligible and show a substantial correspondence between the functioning of the device 1 according to the invention and FIG Calculations of the complex values using program-technical means.

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• 2007
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