EP1831741A2 - Dispositif et procede de redimensionnement optique - Google Patents

Dispositif et procede de redimensionnement optique

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Publication number
EP1831741A2
EP1831741A2 EP05816041A EP05816041A EP1831741A2 EP 1831741 A2 EP1831741 A2 EP 1831741A2 EP 05816041 A EP05816041 A EP 05816041A EP 05816041 A EP05816041 A EP 05816041A EP 1831741 A2 EP1831741 A2 EP 1831741A2
Authority
EP
European Patent Office
Prior art keywords
optical resizing
optical
facet
waveguides
layers
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05816041A
Other languages
German (de)
English (en)
Inventor
Yosi Shani
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
OMS Displays Ltd
Original Assignee
OMS Displays Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by OMS Displays Ltd filed Critical OMS Displays Ltd
Publication of EP1831741A2 publication Critical patent/EP1831741A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/04—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres
    • G02B6/06—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres the relative position of the fibres being the same at both ends, e.g. for transporting images
    • G02B6/08—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres the relative position of the fibres being the same at both ends, e.g. for transporting images with fibre bundle in form of plate
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/04—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres
    • G02B6/06—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres the relative position of the fibres being the same at both ends, e.g. for transporting images
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12166—Manufacturing methods
    • G02B2006/12195—Tapering

Definitions

  • the present invention relates to optics and, more particularly, to a device and method for optical resizing.
  • An electronic display may provide a real image, the size of which is determined by the physical size of the display device, or a virtual image, the size of which may extend the dimensions of the display device.
  • Magnification of images produced by small size image display systems can be performed by projecting the image on a larger screen or via passive optical magnification element providing the user with a magnified virtual image.
  • a virtual image is defined as an image, which cannot be projected onto a viewing surface, since no light ray connects the image and an observer.
  • the image is not projected but rather guided through a bundle of optical fibers extending from a small facet to a large facet.
  • the small facet is oftentimes referred to as "the object plane” whereas the larger facet is oftentimes referred to as "the image plane”.
  • Figures 1-2 are schematic illustrations of several prior art techniques for manufacturing fiber base guided magnifiers.
  • Figures Ia shows an optical image transporting device based on the teachings of U.S. Patent No. 2,825,260. The magnification from the small facet to the large facet is achieved by increasing the separation between the fibers in the bundle.
  • Figure Ib illustrates a modification to this method, disclosed in U.S. Patent Nos. 2,992,587 and 3,853,658. In this technique, the fibers are up-tapered towards the large facet.
  • Figures 2a-b show another technique for producing a fiber optic magnification element, according to the teachings of U.S. Patent Nos. 3,402,000 and 6,326,939.
  • a one-dimensional magnification element includes cylindrically shaped optical fibers which are cut in a manner such that a circular cross section is formed on one side and an elliptic cross section is formed on the other side.
  • the circular cross section is perpendicular to the longitudinal axis of the cylinder, and therefore has the same diameter as the cylinder.
  • the elliptic cross section is slanted with respect to the longitudinal axis, hence has a small axis which equals the diameter of the cylinder and a large axis which is larger than the diameter of the cylinder.
  • a one dimension magnification is established in the direction of the large axis of the elliptic cross section.
  • two such one-dimensional magnification elements are connected via a redirecting layer such that the output of one element is used as the input of the other element.
  • a second redirecting layer is used for coupling the light out of the second magnification element.
  • the cross section of the fibers on the input side of the second element must have the same elliptic cross section of the fibers on the output side of the first element.
  • the elliptic input cross section of the second element's fibers cannot be obtained by slanted cut because the input cross section of the fibers must be perpendicular to their longitudinal axis.
  • a fiber bundle with elliptically shaped fibers does not exist. Therefore, in order not to loose resolution at the second magnification, the number of fibers in the second element should be larger than the number of fibers in the first element, by a factor which equals the one dimensional magnification ratio of the first element. Additional drawbacks of this technique are the need for redirecting layers and the presence of non-guided light which can diminish the display aspect ratio.
  • U.S. Patent Nos. 5,511,141 and 5,600,751 disclose a reading magnifier formed by a bundle of juxtaposed longitudinally tapered optical fibers.
  • the magnifier is commercially available under the trade name TaperMagTM from Taper Vision Co. Ltd., USA [E. PeIi, W.P. Siegmund "Fiber-optic reading magnifiers for the visually impaired," J Opt Soc Am A 12(10): 2274-2285, 1995].
  • the TaperMagTM is bulky (thickness of about 5 cm for only x2 magnification up to a 2 inches screen) because its thickness must be comparable to the size of facet diameter.
  • Kawashima et al. discloses a magnifier which utilizes high-refractive-index regions extending from the small facet to the large facet.
  • Kawashima et al. it was found that a 30 inches magnifier can have a thickness of less than 4 cm and perform ten times enlargement.
  • the manufacturing process of Kawashima's magnifier is, however, rather complicated.
  • one embodiment of Kawashima et al. involves the alignment of dozens of laminated thin plates produced by masks with increasing core dimensions.
  • Another embodiment of Kawashima et al. involves three dimensions fiber handling.
  • Kawashima et al. also teach simpler manufacturing processes, these are limited to magnification ratio of 2 or less. There is thus a widely recognized need for, and it would be highly advantageous to have a device and method for optical resizing, devoid of the above limitations.
  • an optical resizing device comprising: a first optical resizing element having a plurality of waveguides designed and constructed to provide optical resizing in a first dimension; and a second optical resizing element, having a plurality of waveguides designed and constructed to provide optical resizing in a second dimension.
  • the second optical resizing element is coupled to the first optical resizing element such that light exiting the first optical resizing element enters the second optical resizing element, hence being resized in both the first and the second dimensions.
  • the waveguides of at least one of the first and second optical resizing elements are at least partially tapered. According to further features in preferred embodiments of the invention described below, the plurality of waveguides of at least one of the first optical resizing element and the second optical resizing element are formed and/or embedded in a substrate in a longitudinally expanding arrangement such as to provide the optical resizing.
  • the longitudinally expanding arrangement comprises layers of waveguides, each layer being arranged such that the waveguides extend from a first region of the layer to a second region of the layer thereby defining a circumferential boundary within the layer, wherein the length characterizing the circumferential boundary is smaller at the first region than at the second region, such as to provide the optical resizing.
  • an optical resizing element comprises a plurality of layers forming a substrate having a first facet and a second facet being larger than the first facet.
  • Each layer has an arrangement of substantially parallel waveguides formed and/or embedded in the layer and extending from a first region of the layer to a second region of the layer.
  • the layers are arranged in a partially overlapping optical arrangement whereby the second region of each layer is optically exposed at the second facet such as to provide optical resizing in one dimension.
  • an optical resizing element there is provided an optical resizing element.
  • the optical resizing element comprises a substrate formed of at least one layer, each layer has an arrangement of waveguides formed and/or embedded in the layer and extending from a first region of the layer to a second region of the layer thereby defining a circumferential boundary within the layer.
  • the length characterizing the circumferential boundary is smaller at the first region than at the second region, such as to provide optical resizing in one dimension.
  • the first region and the second region are located at opposite sides of the layer.
  • first region and the second region are located at adjacent sides of the layer.
  • first region and the second region are located at the same side of the layer. According to still further features in the described preferred embodiments the first region and the second region are substantially parallel.
  • first region and the second region are substantially orthogonal.
  • first region and the second region are substantially collinear.
  • At least one of the optical resizing elements comprises a slanted layer for providing the optical resizing.
  • At least one of the optical resizing elements comprises a terrace for providing the optical resizing.
  • At least one of the optical resizing elements is designed and constructed such that the light enters the optical resizing element while propagating in a first direction and exit the optical resizing element while propagating in the same direction.
  • At least one of the optical resizing elements is designed and constructed such that the light enters the optical resizing element while propagating in a first direction and exit the optical resizing element while propagating in a second direction being different from the first direction.
  • the second facet is substantially parallel to the first facet. According to still further features in the described preferred embodiments the second facet is substantially orthogonal to the first facet.
  • the second facet is tilted with respect to the first facet.
  • the second facet and the first facet are substantially coplanar.
  • one optical resizing element is constructed and designed to receive light from a plurality of sources and transmitting the light into another optical resizing element.
  • the device further comprises at least one additional optical resizing element which receives light from at least one additional light source and transmits the light into the second optical resizing element.
  • the additional light source(s) comprises a monochrome light source.
  • the optical resizing element being designed and constructed to emit light to a plurality of directions.
  • the light can be originated from different sources, in which case each direction is attributed to a different source.
  • the light can also be originated from a single source or another optical resizing element, in which case the same light is being emitted to a plurality of directions. For example, a single image can be formed on two different facets of the device.
  • the device further comprises at least one additional optical resizing element positioned at one of the at least two different directions and configured to receive light from the first optical resizing element.
  • At least one of the optical resizing elements comprises a plurality of partial optical resizing elements whereby each partial optical resizing element is designed and constructed to provide partial optical resizing in a respective dimension.
  • the device or optical resizing element further comprises a diffusive layer attached to or etched in the second facet.
  • the device or optical resizing element further comprises an expanding structure.
  • the expanding structure comprises a holographic optical element. According to still further features in the described preferred embodiments the expanding structure comprises a stack of layers alternately patterned with high refractive index regions and low refractive index regions.
  • the expanding structure comprises a stack of layers patterned with grooves. According to still further features in the described preferred embodiments the expanding structure comprises a stack of layers of tapered waveguides.
  • the expanding structure comprises mirrors.
  • the mirrors comprise total internal reflection mirrors.
  • the mirrors are coated by high reflection coat.
  • the expanding structure comprises Bragg reflectors.
  • At least one optical resizing element is designed and constructed to polarize light.
  • an optical resizing device comprising a plurality of layers forming a substrate having a first facet and a second facet, the plurality of layers being arranged in a partially overlapping optical arrangement.
  • Each layer has an arrangement of waveguides formed and/or embedded in the layer and extending from a first region of the layer to a second region of the layer thereby defining a circumferential boundary within the layer.
  • the length characterizing the circumferential boundary is smaller at the first region than at the second region, and the second region is optically exposed at the second facet.
  • the first facet is defined by ends of overlapping regions of the plurality of layers.
  • each layer is partially exposed at the first facet.
  • At least a few layers comprise mirrors for redirecting light propagating within the plurality of waveguides out of the layer.
  • at least a portion of the mirrors are total internal reflection mirrors.
  • at least a portion of the mirrors are etched mirrors.
  • at least a portion of the mirrors are coated by a high reflective coat.
  • At least a portion of the mirrors comprise planar facet.
  • At least a portion of the mirrors comprise non-planar facet.
  • at least a few layers comprise Bragg reflectors for redirecting light propagating within the plurality of waveguides out of the layer.
  • At least a few layers comprise holographic optical elements for redirecting light propagating within the plurality of waveguides out of the layer.
  • the device is characterized by a field-of-view selected sufficiently small so as to substantially preserve brightness of light being resized by the device.
  • a method of manufacturing an optical resizing element comprises: (a) forming on a substrate a plurality of waveguides in an expanding arrangement extending from a first region of the substrate to a second region of the substrate, thereby providing a layer of waveguides; (b) repeating the step (a) a plurality of times, thereby providing a plurality of layers; and (c) stacking the plurality of layers so as to form a first facet, defined by ends of the plurality of layers, and a second facet, defined by an exposed surface of one of the plurality of layers; thereby manufacturing the optical resizing element.
  • the method further comprises: (d) forming on a substrate a plurality of substantially parallel waveguides extending from a first region of the substrate to a second region of the substrate, thereby providing a layer of waveguides; (e) repeating the step (d) a plurality of times, thereby providing a plurality of layers; (f) stacking the plurality of layers in a partially overlapping optical arrangement whereby the second region of each layer is optically exposed, so as to form a first facet and a second facet, the second facet being defined by optically exposed portion of the plurality of layers; thereby manufacturing a second optical resizing element; and (g) optically coupling the optical resizing element to the second optical resizing element so as to allow propagation of light from the optical resizing element to the second optical resizing element, wherein the light is resized in a first dimension within the optical resizing element and in a second dimension within the second optical resizing
  • a method of manufacturing a plurality of optical resizing elements comprises: (a) forming on a substrate a plurality of waveguides extending from a first region of the substrate to a second region of the substrate, thereby providing a layer of waveguides; (b) repeating the step (a) a plurality of times, thereby providing a plurality of layers; (c) stacking the plurality of layers so as to provide a stack; and (d) performing at least one cut to the stack so as to provide a plurality of optical resizing elements.
  • a method of manufacturing an optical resizing element comprises: (a) forming on a substrate a plurality of parallel waveguides extending from a first region of the substrate to a second region of the substrate, thereby providing a layer of waveguides; (b) repeating the step (a) a plurality of times, thereby providing a plurality of layers; and (c) stacking the plurality of layers in a partially overlapping optical arrangement whereby the second region of each layer is optically exposed, so as to form a first facet and a second facet, the second facet being defined by optically exposed portion of the plurality of layers; thereby manufacturing the optical resizing element.
  • the method further comprises: (d) repeating the steps (b)-(c) so as to form a second optical resizing element; and (e) optically coupling the optical resizing element to the second optical resizing element so as to allow propagation of light from the optical resizing element to the second optical resizing element, wherein the light is resized in a first dimension within the optical resizing element and in a second dimension within the second optical resizing element.
  • the method comprises: (a) forming on a substrate a plurality of waveguides extending from a first region of the substrate to a second region of the substrate thereby defining a circumferential boundary within the substrate, wherein the length characterizing the circumferential boundary is smaller at the first region than at the second region; (b) repeating the step (a) a plurality of times, thereby providing a plurality of layers; and (c) stacking the plurality of layers in a partially overlapping optical arrangement whereby the second region of each layer is optically exposed, so as to form a first facet and a second facet, the second facet being defined by optically exposed portion of the plurality of layers, thereby manufacturing the optical resizing device.
  • the method further comprises positioning mirrors for redirecting light propagating within the plurality of waveguides out of the substrate.
  • the method further comprises cutting the layers, subsequently to the step of stacking the layers, so as to form at least one of the first facet and the second facet.
  • the method is performed such that at least one facet is slanted.
  • the method further comprises cutting the plurality of layers, prior to the step of stacking the layers, so as to form, for each layer, a layer end exposing a plurality of waveguides ends.
  • the method further comprises depositing a polarizer on at least a portion of the layers, prior to the step of stacking the layers.
  • the method further comprises coupling at least one facet to a coupler.
  • the coupler comprises a microlens array.
  • the method further comprises etching at least one facet so as to form a microlens array on the facet.
  • At least a few of the waveguides are tapered or partially tapered.
  • the tapering is characterized by a smooth profile. According to still further features in the described preferred embodiments the tapering is characterized by a substantially stepped profile.
  • the plurality of layers are partially exposed at the second facet.
  • At least a few of the plurality of waveguides form a planar light circuit.
  • At least a few of the plurality of waveguides form an optical fibers array.
  • At least a few of the plurality of waveguides are single mode waveguides. According to still further features in the described preferred embodiments the waveguides are multimode waveguides.
  • the optical resizing device or element further comprises light absorbers introduced between cores of the waveguides.
  • at least a few waveguides comprise a core and a cladding the core having a higher refractive index than the cladding.
  • at least a few waveguides comprise photonic bandgap material.
  • the optical resizing device or element further comprises a microlens array for coupling the light into the optical resizing device or optical resizing element.
  • the optical resizing device or element further comprises at least one fiber bundle for coupling the light into the optical resizing device or element.
  • the optical resizing device or element are flexible.
  • optical resizing device or element are foldable.
  • the optical resizing device or element serves as a component in a display system. According to still further features in the described preferred embodiments the optical resizing device or element serves as a component in a autostereoscopic display system.
  • a method of resizing a spot of light comprising, transmitting the light through the optical resizing device of any of the preceding aspects or features.
  • the method further comprising distorting the spot of light such as to provide a brightness gradient thereacross thereby compensating non homogenous optical losses.
  • the method wherein the light constitutes an image.
  • the method further comprising distorting the image such as to provide a brightness gradient thereacross thereby compensating non homogenous optical losses.
  • the present invention successfully addresses the shortcomings of the presently known configurations by providing an optical resizing element, optical resizing device and method enjoying properties far exceeding the prior art.
  • FIGs. la-2b are schematic illustrations of prior art techniques for manufacturing fiber based guided magnifiers.
  • FIGs. 3a-c are schematic illustrations of a longitudinally expanding arrangement of waveguides (Figure 3a), a partially tapered waveguide (Figure 3b) and a longitudinally expanding arrangement of partially tapered waveguides (Figures 3c), according to various exemplary embodiments of the present invention.
  • FIG. 3d is a schematic illustration of the embodiment of Figure 3c with more than one layer.
  • FIGs. 4a-i are schematic illustrations of an optical resizing element, in various exemplary embodiments of the invention.
  • FIG. 5 is a schematic illustration of an optical resizing device having two optical resizing elements, in various exemplary embodiments of the invention.
  • FIG. 6a is a schematic illustration of a small facet of a receiving optical resizing element, in various exemplary embodiments of the invention.
  • FIG. 6b is a three-dimensional illustration of the waveguides of the element of Figure 6a, in various exemplary embodiments of the invention.
  • FIG. 7a is a three-dimensional schematic illustration of the device in the embodiment in which the entry and exit facets of each optical resizing element are substantially orthogonal to each other.
  • FIG. 7b is a three-dimensional schematic illustration of the device on Figure 7a, in a preferred embodiment in which two pairs of optical resizing elements are employed.
  • FIG. 8 is a schematic illustration of the device in a preferred embodiment in which the facets of one optical resizing element are substantially parallel and the facets of the other optical resizing element are substantially orthogonal.
  • FIG. 9 is a schematic illustration of device in a preferred embodiment in which the facets of the optical resizing elements are substantially coplanar.
  • FIGs. 10a-b are schematic illustrations of a photomask layout for manufacturing an arrangement of waveguides, according to various exemplary embodiments of the present invention.
  • FIGs. l la-b are schematic illustrations of process for manufacturing waveguides which are tapered both vertically and laterally.
  • FIGs. 12a-f are schematic illustrations of an optical resizing device in preferred embodiments in which a plurality of light sources are employed;
  • FIGs. 13a-c are schematic illustrations of the device in preferred embodiments in which there is more than one optical output from the device.
  • FIGs. 14a-b are schematic illustrations of the device in preferred embodiments in which the device comprises one or more additional optical elements.
  • FIG. 15 is a schematic illustration of a layer of the optical resizing element in a preferred embodiment in which the layer comprises a polarizer.
  • FIGs. 16a-b are schematic illustrations of the coupling between the device and a light source, in the preferred embodiment in which the light source is an image source.
  • FIG. 17 is a schematic illustration of a preferred embodiment in which an input image is focused on device using a lens.
  • FIGs. 18a-b are schematic illustrations of the coupling between the device and a light source, in the preferred embodiment one or more fiber bundles are employed.
  • FIG. 19 is a schematic illustration of one layer of the optical resizing element in a preferred embodiment in which the waveguides are tilted with respect to the layer's end.
  • FIGs. 20-22f are schematic illustration of an optical resizing device, in preferred embodiments in which the device is manufactured according to the principle of partially overlapping optical arrangement.
  • FIGs. 23a-b are schematic illustrations of a side view ( Figure 23a) and a top view ( Figure 23b) of a portion of a facet of device similar to the device of Figures 20- 22 in a preferred embodiment in which the facet has a two-dimensional stepped shape.
  • FIGs. 23c-d are schematic illustrations of mirror shapes, according to various exemplary embodiments of the present invention.
  • FIGs. 24a-e are schematic illustrations of a side view of an optical resizing element with a two-dimensional stepped or slanted profile, according to various exemplary embodiments of the present invention.
  • FIG. 25 is a schematic illustration of a foldable optical resizing device, according to a preferred embodiment of the present invention.
  • FIGs. 26a-b is a schematic illustration of configurations in which light is coupled out from the device via an arrangement of transmitting elements, according to various exemplary embodiments of the present invention.
  • FIGs. 27a-b are schematic illustrations of process for manufacturing slanted optical resizing element, in various exemplary embodiments of the invention.
  • FIGs. 27c-h are schematic illustrations of an expanding structure, according to various exemplary embodiments of the present invention.
  • FIGs. 28a-c are schematic illustrations of a top view ( Figures 28a-b) and a side view ( Figure 28c) of layers of a device similar to the device of Figure 20-22 in a preferred embodiment in which the layers are low-weight layers.
  • FIGs. 29a-e are schematic illustrations of a preferred folding technique for manufacturing a device similar to the device of Figure 20-22, according to various exemplary embodiments of the present invention.
  • FIGs. 30a-b are schematic illustrations of a simultaneous process for manufacturing a plurality of optical resizing elements, in various exemplary embodiments of the invention.
  • FIG. 31 is a schematic illustration of a device similar to the device of Figure
  • the device receives light from a plurality of sources.
  • FIGs. 32a-b are schematic illustrations of a top view ( Figure 32a) and a cross sectional view ( Figure 32b) of a device similar to the device of Figure 20-22 in a preferred embodiment in which the device receives optical input in the form of a plurality of monochromatic light sources.
  • FIGs. 33a-c are schematic illustration of techniques for coupling light out of the layers of a device similar to the device of Figure 20-22, according to various exemplary embodiments of the present invention.
  • FIGs. 34a-35c are schematic illustrations of a device similar to the device of Figure 20-22 in a preferred embodiment in which the device is used to provide an autostereoscopic image.
  • FIG. 36 is a schematic illustration of different optical regions in the field-of- view of a device similar to the device of Figures 34a-35c.
  • FIGs. 37a-b are schematic illustrations of one layer ( Figure 37a) and the resulting field-of-view ( Figure 37b) in the preferred embodiment in which a plurality of autostereoscopic images are provided.
  • FIG. 38 is a schematic illustration of the optical resizing device in a preferred embodiment in which the input image has a non uniform brightness so as to compensate differential waveguide losses.
  • FIG. 39a is a schematic illustration of a layer of the optical resizing element in a preferred embodiment in which the layer comprises light absorbers.
  • FIG. 39b is a schematic illustration of waveguides with variable cross-sections, according to a preferred embodiment of the present invention.
  • FIG. 40 is a schematic illustration a procedure for improving the brightness of the output light, in various exemplary embodiments of the invention.
  • FIG. 41 is a schematic illustration of a procedure for modifying the field-of- view of the device, in various exemplary embodiments of the invention.
  • the present embodiments comprise method, optical element and device which can be used for optical resizing. Specifically, but not exclusively, the present invention can be used to provide optical resizing in various applications such as display systems and the like.
  • optical resizing refers to the expansion or contraction of an optical wavefront, which can be, for example, a planar light spot.
  • optical resizing refers to the change (expansion or contraction) in the area occupied by the optical wavefront.
  • the optical resizing refers to the magnification or reduction of the image, which can be effected by separation changes or size changes of picture elements (e.g., pixels) of the image.
  • the size of the area occupied by the optical wavefront is interchangeably referred to herein as the transverse area of a light beam.
  • the present embodiments exploit the technology of embedded waveguides to provide optical resizing.
  • the embedded waveguides can be of any type known in the art, such as waveguides of Planar Light Circuits (PLC) or other arrays. Additionally, the waveguides can be single mode or multimode waveguides. The cross-section of the waveguides can be generally round, generally rectangular, or of any other geometrical figure.
  • the embedded waveguides are arranged in one or more layers so as to allow their manufacturing in a layerwise fashion.
  • the optical resizing can be achieved by an optical resizing element made of a bulk material as further detailed hereinunder.
  • the light can enter or exit the layers either through their surface or through their end as further detailed hereinunder.
  • the optical resizing of the present embodiment can be achieved by longitudinally expanding arrangements of waveguides of any type and shape. More specifically, the longitudinally expanding arrangements can comprise tapered waveguides, partially tapered waveguides, non-tapered waveguides or any combination thereof.
  • Figures 3a-c illustrate a longitudinally expanding arrangement of non-tapered waveguides (Figure 3 a), a partially tapered waveguide (Figure 3 b) and a longitudinally expanding arrangement of partially tapered waveguides, (Figures 3c), according to various exemplary embodiments of the present invention.
  • Figure 3d exemplifies the embodiment of Figure 3c with more than one layer.
  • each or some of the waveguides can comprise several sections interconnected via mirror corners. Such design can be used to reduce or eliminate waveguide bends hence to reduce the thickness of the final product.
  • An additional advantage of the present embodiments is that the PLC technology allows the fabrication of waveguides with rectangular core cross section, thereby increasing the filling factor and reducing coupling losses.
  • embedded waveguides allows the fabrication of flexible elements which can be easily assembled.
  • an optical device can be assembled with partially overlapping flexible layers, whereby instead or in addition to the bending of the individual waveguides, an entire layer can be bended.
  • a layerwise production process facilitates the manufacturing of foldable optical devices, whereby different layers are only partially attached thereamongst.
  • an optical resizing element generally referred to herein as element 10.
  • Element 10 comprises a substrate 12 formed of one or more layers 14.
  • Each layer of element 10 has an arrangement of waveguides formed and/or embedded therein.
  • the arrangement of waveguide in each layer is a longitudinally expanding arrangement.
  • Figure 4b is a schematic illustration of a layer 14 of element 10.
  • Layer 14 preferably comprises a plurality of waveguides 16 extending from a first region 18 to a second region 20 of layer 14 thereby defining a circumferential boundary 22 within layer 14.
  • Boundary 22 is illustrated as a dash line in Figure 4b.
  • first 18 and second 20 regions are substantially parallel and located at opposite sides of layer 14.
  • regions 18 and 20 can have any geometrical relation therebetween.
  • regions 18 and 20 can be located at adjacent sides of layer 14 (e.g., in substantially orthogonal relation) or at the same side of layer 14 (e.g., in substantially collinear relation or substantially parallel offset relation).
  • substantially parallel refers to a relative orientation of less than 20°, more preferably less than 10°, most preferably less than 5°, say about 0°.
  • parallel as used herein is to be understood as substantially parallel.
  • substantially orthogonal refers to a relative orientation of from about 70° to about 110°, more preferably from about 80° to about 100°, most preferably from about 85° to about 95°, say about 90°.
  • substantially collinear refers to a relative orientation of less than 20°, more preferably less than 10°, most preferably less than 5°, say about 0°.
  • substantially parallel offset refer to a case where the facets are substantially parallel but are also substantially offset by less than 50mm, more preferably less than lmm, most preferably less than 0.1mm, say about 0.01mm.
  • the waveguides are shown to have a substantial linear shapes, this need not necessarily be the case, since, for some applications, it may be desired to have non-linear (i.e., curved) shapes. Additionally, the waveguides can be formed of non continuous sections interconnected by corner mirrors as further detailed hereinunder.
  • the length characterizing boundary 22 is smaller at first region 18 than at second region 20.
  • One of ordinary skill in the art will appreciate that such arrangement provides optical resizing in one dimension defined by regions 18 and 20 of the layer. For example, when a light beam enters layer 14 from first region 18, propagate through waveguides 16 and exits from second region 20 its transverse area is expanded in a direction substantially parallel to regions 18 and 20. Conversely, when the light beam enters layer 14 from second region 20 and exits from first region 18 its transverse area is reduced in the direction parallel to regions 18 and 20.
  • Figures 4c-d are schematic illustrations of facets of element 10 in a preferred embodiment in which the layers are stacked such that the smaller regions of the layers form a small facet 24 and the larger regions of the layers form a large facet 26.
  • the waveguides can be tapered such that the resizing is achieved due to both the longitudinally expanding arrangement and the tapering of the individual waveguides.
  • Figure 4e is a schematic illustration of a preferred embodiment in which tapered waveguides are employed in a configuration in which first region 18 is substantially orthogonal to second region 20. Still, the length characterizing boundary 22 is smaller at first region 18 than at second region 20, so as to ensure the optical resizing.
  • Figure 4f is a schematic illustration of a preferred embodiment in which tapered waveguides are employed in a configuration in which first region 18 is collinear with second region 20.
  • small facet 24 and large facet 26 can have any geometrical relations therebetween.
  • Figures 4g-i schematically illustrate several geometrical relations between facets 24 and 26, according to various exemplary embodiments of the present invention.
  • Waveguides suitable for the present embodiments can have a core of high refractive index and cladding of lower refractive index, or they can comprise photonic bandgap materials.
  • layers of waveguides suitable for the present embodiments can be manufactured, for example, by etching grooves in layers of a low refractive index material serving as the waveguide cladding, and depositing a high refractive index material serving as the waveguide core, into the grooves.
  • the waveguide core can be subsequently coated by an additional layer of low refractive index serving as a top cladding layer.
  • Photonic bandgap material waveguides can be manufactured by forming (e.g., etching) optical periodic structures on a substrate of dielectric material, leaving stripes serving as the core waveguide, with no periodic structure.
  • the optical periodic structures are characterized by spatially periodic variations in the refractive index with cycles in the sub-micrometer to micrometer range, which define a wavelength band in which no propagation of light occurs (photonic bandgap).
  • the optical periodic structures can then be coated by a cladding layer.
  • the advantage of using photonic bandgap materials is that there is no radiation loss in the photonic bandgap, even in waveguides sections of high curvature.
  • the PLC polymer lithography technology is employed (see, e.g., Eldada et al., "Advances in polymer integrated optics," IEEE J. Selected Topics in QE, vol. 6, 54-68, 2000).
  • Contemplated processes for fabricating the layers of waveguides include also, without limitation, the Photobreaching process [Gallo et ah, "High-density interconnects for 2-dimensional VCSEL arrays suitable for mass scale production," ITCom 2001, paper 4532-47, 2001], the casting/molding process [Kopetz et al., "Polysiloxane optical waveguide layer integrated in printed circuit board," Elec. Lett. Vol.
  • the waveguides of the present embodiments can also be arrays of optical fibers embedded in the layers by means of adhesive materials, preferably without external frame, as known in the art (to this end see, e.g., U.S. Patent Nos. 5,381,506, 6,597,845 6,885,800).
  • the optical element of the present embodiments preferably comprises many layers of waveguides.
  • the number of layers is of the order of a several hundreds (e.g., about 500 layers) to several thousands of layers (e.g., about 5000 layers).
  • the layers can be stacked together by processing a polymer wafer layer after layer or by stacking together laminated layers.
  • the layers can also be stacked using a combination of these techniques. Once the wafer layers are stacked, the wafer is sawed to stripes and the required facets are polished. Alternatively, the stripes can be sawed before stacking. It will be appreciated that since the optical resizing element is wide and short, many such elements can be fabricated in a parallel process.
  • the present embodiments successfully provide an optical resizing device which provides optical resizing in two-dimensions, preferably two substantially orthogonal dimensions.
  • two- dimensional optical resizing is achieved by assembling several optical resizing elements which are similar in their principles and operations (but not necessarily in size) to element 10.
  • two- dimensional optical resizing is achieved by modification of element 10. Following is a description of preferred embodiments in which several optical resizing elements are assembled. Description of the preferred embodiments in which the two-dimensional optical resizing is achieved by modification of element 10 is provided hereinafter.
  • FIG. 5 is a schematic illustration of an optical resizing device 30, according to various exemplary embodiments of the present invention.
  • Device 30 preferably comprises a first optical resizing element 32 which provides optical resizing in a first dimension 36, and a second optical resizing element 34, which provides optical resizing in a second dimension 38.
  • Elements 32 and 34 can each independently operate similarly to element 10 above. Alternatively, one of elements 32 and 34 can be manufactured similarly to element 10 while the other can be manufactured by conventional techniques.
  • element 34 is coupled to element 32 such that light exiting element 32 enters element 34.
  • element 34 serves as a receiving element while element 32 serves as a transmitting element within device 30.
  • the coupling between elements 32 and 34 can be in any way known in the art, such as via direct contact, fiber bundle, or any other optical coupling arrangement. It is advantageous to manufacture the optical resizing elements such that the smaller facet of one element matches the larger facet of the other element. Being manufactured in such manner, one of the optical resizing elements is larger than the other.
  • the first element when device 30 is used for expanding light beam (i.e., the light beam's transverse area is larger at the output than at the input), the first element is smaller than the second element, and when device 30 is used for the contracting light (i.e., the light beam's transverse area is smaller at the output than at the input), the first element is larger than the second element.
  • elements 32 and 34 are manufactured such that light enters the small facet 40 of element 32, expanded along dimension 36, exits element 32 through facet 42 and enters element 34 through facet 44, which preferably has the size as facet 42 of element 32. The light then propagates within element 34, expanded along dimension 38 and exit through large facet 46 expanded in both dimensions.
  • element 32 and 34 are manufactured similarly to element 10, they can be processed using the same photomask layout (such as, for example, the photomasks shown in Figures 3a, 3c, 4e and 4f) but different layer thickness.
  • element 32 can be formed of thinner layers defining the large facet illustrated in Figure 4d above (see also the three-dimensional illustration of Figure 3d) while element 34 can be formed of thicker layers defining the small facet illustrated in Figure 6a.
  • a three-dimensional illustration of the waveguides of element 34 according to the presently preferred embodiment of the invention is shown in Figure 6b.
  • Figure 7a is a three-dimensional schematic illustration of device 30 in the embodiment in which the entry and exit facets of each optical resizing element are substantially orthogonal to each other.
  • small facet 40 is substantially orthogonal to large facet 42
  • small facet 44 is substantially orthogonal to large facet 46.
  • Facet 42 and facet 44 are parallel and preferably in contact to allow optical coupling between element 32 and element 34. It will be appreciated that when this embodiment is used to transmit an image the image exiting device 30 is a mirror image of the original image.
  • the advantages of the embodiment shown in Figure 7a are that there are less waveguide bends 48 and there is no scattered light from the propagating beam toward the large facet.
  • device 30 can comprise two or more pairs of optical resizing elements whereby each pair functions according to the above description; namely, one element of the pair provides the optical resizing in one dimension and the other element of the pair provides the optical resizing in other dimension.
  • This embodiment is particularly useful when high magnification or reduction is required or in order to avoid dealing with high aspect ratio waveguides during the fabrication process. For example a 30 times magnification can be achieved with two pairs of optical resizing elements, whereby the first pair provides 3 times magnification (in two dimensions) and the second pair provides 10 times magnification (in two dimensions).
  • FIG. 7b A representative example of the presently preferred embodiment of the invention is illustrated in Figure 7b, for the case in which two pairs of optical resizing elements 32, 33, 34 and 35 are employed.
  • element 33 expands a light beam 72 in one dimension (say, along the x direction) to provide expanded light beam 74
  • element 35 expands light beam 74 in another dimension (say, along the y direction) to provide an expanded light beam 76
  • elements 32 expands light beam 76 in one dimension (say, along the JC direction) to provide expanded light beam 78
  • elements 34 expands light beam 78 in another dimension (say, along the y direction) to provide expanded light beam 80.
  • Original light beam 72 is therefore expanded twice along the x direction and twice along the y direction.
  • each layer of the optical resizing element of the present embodiments can be formed using a photomask which is similar to the photomask illustrated in Figure 4e, above.
  • the waveguide bends 48 shown in Figures 7a-b can be replaced with the corner mirrors 50 (see Figure 4e) so as to further reduce the thickness of the optical resizing elements.
  • Figure 8 is a schematic illustration of device
  • facets 40, 42, 44 and 46 are coplanar.
  • the waveguides of each layer of the optical resizing element can be formed using a photomask which is similar to the photomask illustrated in Figure 4f, above, whereby regions 18 and 20 are collinear.
  • a light beam 92 enters small facet 40 of element 32, propagates with element 32, experience a 180° change in direction and exit facet 42 expanded along first dimension 36.
  • the (expanded) light beam exiting facet 42 is designated in Figure 9 by numeral 94.
  • Expanded light beam 94 enters small facet 44 of element 34, propagates with element 34, experiences an additional expansion along dimension 38 and an additional 180° change in direction, and exit facet 46 expanded along both dimensions 36 and 38.
  • the light beam exiting facet 46 is designated by numeral 96.
  • the light passing through device 30 thus experiences two expansions, one in each dimension, and two propagation flips. To this effect, the light exits device 30 propagating along its original direction and being expanded in two dimensions.
  • the more detailed reference in the above description to specific propagation directions of the exiting light beam is not intended to limit the scope of the present invention to any entry-exit angular relations.
  • the angle between the entry and exit propagation directions of the light can be 0°, 90°, 180° or any other angle.
  • the entry-exit angular relation depends on the orientation of the waveguides relative to the facets of the optical resizing elements.
  • the light may enter any of the optical resizing elements of device 30 at a right angle to the surface of the input facet and be emitted at a non-right angle from the output facet.
  • the light may enter any of the optical resizing elements of device 30 at a right angle to the surface of the input facet and be emitted at a non-right angle from the output facet.
  • such configuration corresponds to an entry-exit angle which is other than 0°, 90° or 180°.
  • the thickness of each optical resizing element can be rather small due to the expanding arrangement of the waveguides. This thickness can be further reduced by down-tapering the waveguides at predetermined sections of each layer.
  • Representative examples of the thickness of the optical resizing element of the present embodiments include, without limitation, a thickness of from about 0.1 mm to about 100 mm, more preferably, from about 1 mm to about 10 mm.
  • Figures 10a-b are schematic illustrations of a photomask layout for manufacturing an arrangement of waveguides, according to various exemplary embodiments of the present invention.
  • Figures 10a-b illustrate the preferred embodiments in which regions 18 and 20 are parallel and located at opposite sides of the layer.
  • regions 18 and 20 are parallel and located at opposite sides of the layer.
  • the waveguides are down-tapered and squeezed before they are up-tapered and expanded towards region 20.
  • the down-tapering is advantageous, firstly because it can further reduced the thickness of each optical resizing element, and secondly because it allows the separation between the parallel waveguides so as to reduce or eliminate crosstalk.
  • the thickness of device 30 is mainly dictated by the waveguide separation S y , see Figure 10b.
  • the thickness can be approximated by the expression 0.5 S y (N ⁇ + N 2 ) where NiXN 2 is the number of waveguides (for example, when device 30 is used for resizing an image, NjXN 2 can be the number of pixels in the image).
  • the thickness of the optical resizing element is dictated by the input pixels array size. If waveguide bends 48 are employed (rather than corners mirrors 50), then the bend radius should be added to the overall thickness of the element. However, as further detailed hereinunder, parasitic losses are preferably added to the shorter waveguides by reducing the bend radius. Thus, the thickness of device 30 can be dictated by the bend radius, irrespectively of the number of pixels/waveguides.
  • the waveguides can be vertically tapered at the input and output facets.
  • vertical tapering is a well known technology (see, e.g., T. Bakke, et al. "Polyene optical spot-size transformer with vertical and lateral tapers," J. Light. Tech., vol 20, 1188-1197, 2002).
  • a process of manufacturing waveguides which are tapered both vertically and laterally is illustrated in Figures l la-b for a single waveguide ( Figure Ha) and a stack of waveguides ( Figure l ib).
  • device 30 receives light from a plurality of sources.
  • the use of more light sources can reduce the thickness of device 30; thickness can be reduced since the number of parallel waveguide from the input facet to the output facet is reduced.
  • the thickness reduction factor equals the number of input light sources employed. For example, for two light sources the thickness can be halved.
  • each individual light source can have lower resolution (fewer pixels) while preserving the desired brightness.
  • An additional advantage is that the use of plurality of sources can facilitate production of three- dimensional images, as further detailed hereinunder.
  • Receiving light from multiplicity of sources can be achieved in more than one way.
  • two light rays 122 and 124 enter first optical resizing element 32 from two different light sources (not shown), but any number of light sources can be employed.
  • element 32 is manufactured in accordance with the embodiment in which regions 18 and 20 (not shown) are collinear, but this need not necessarily be the case because, as will be appreciated by one of ordinary skill in the art, several light beam can be inputted to element 32 also in other cases.
  • element 32 comprises two input facets, designated 40a and 40b, and one output facet 42.
  • the number of input facets of element 32 are preferably adjusted accordingly (i.e., three input facets for three light sources, etc.). Both light beams exit element 32 through facet 42 expanded in one dimension and enter element 34 through facet 44 where they are expanded in the other dimension as further detailed hereinabove.
  • device 30 comprises two optical resizing elements, designated 32a and 32b, both serving as transmitting elements within device 30, and one optical resizing element, designated 34 serving as receiving element within device 30.
  • Figure 12b is for the embodiment in which each of optical resizing elements 32a and 32b is manufactured in accordance with the embodiment in which regions 18 and 20 (not shown) are collinear
  • Figure 12c is for the embodiment in which each of optical resizing elements 32a and 32b is manufactured in accordance with the embodiment in which regions 18 and 20 are located on adjacent sides of the layer. All combinations between the above embodiments are also contemplated.
  • device 30 receives optical input in the form of a plurality of monochromatic light sources and uses the optical input to produce a resized chromatic light beam.
  • a plurality of monochromatic images can be magnified and combined by device 30 to provide a magnified chromatic image.
  • three monochromatic images ⁇ e.g., a red image a green image and a blue image
  • three monochromatic image sources (not shown) to enter three optical resizing elements 32a 32b and 32c, respectively.
  • Each of elements 32a, 32b and 32c magnifies the respective monochromatic image in one dimension and transmits it to element 34.
  • Element 34 magnifies the monochromatic images and combines them in the other dimension to provide a magnified chromatic image.
  • element 34 is preferably manufactured from an alternating sequence of layers, whereby the waveguides of each layer are preferably optimized according to the average wavelength of one monochromatic image.
  • Shown in Figure 12d are three types of layers, designated by numerals 37a, 37b and 37c. Layers 37a, 37b and 37c can be optimized, for example, to typical average wavelengths of red, green and blue monochromatic images, respectively.
  • the length of the waveguides is selected according to the position of elements 32a, 32b and 32c relative to element 34.
  • Figure 12e is a schematic illustration of layers 37a, 37b and 37c in the alternating sequence, for the case of red, green and blue images.
  • This embodiment is advantageous because the use of wavelength specific waveguides reduces or eliminates possible dispersion.
  • An additional advantage of this embodiment is that the image source can have less optical elements such as lenses and multiplexers. Thus, instead of being built at the input source with multiplexers and lenses, the image source is multiplexed at element 34.
  • Elements 32a, 32b and 32c, which, as stated receive and transmit monochromatic images, can all be manufactured using similar or identical photomasks, see, e.g., the photomask illustrated in Figure 12f.
  • the present embodiments are suitable for imagery optical data as well as non imagery optical data and the more detailed reference to imagery data is not to be interpreted as limiting the scope of the invention in any way.
  • the present embodiments can be used to provide a chromatic image or a chromatic back illumination for another display device, e.g., LCD panel with a stripe matrix of red-green-blue (RGB) light from three filtered light source, LEDs or laser sources.
  • RGB red-green-blue
  • optical resizing element 32 transmits light to more than one direction. Shown in Figure 13a are three optical resizing element, 32 34a and 34b whereby element 32 transmits light to both elements 34a and 34b.
  • element 32 serves as a transmitting element within device 30 and elements 34a and 34b both serve as receiving elements within device 30.
  • a light beam 132 enters element 32 and being transmitted thereby in the form of two light beams 134a and 134b. It is to be understood that element 32 can transmit more than two (e.g., three, four) light beams.
  • At least one, more preferably both light beams 134a and 134b are independently resized (e.g., expanded) in one dimension with respect to light beam 132.
  • beams 134a and 134b can be a three time magnification image and a two time magnification image of the original image, respectively.
  • one beam can be a magnification image of the original image and the other can be a reduction thereof.
  • Elements 34a and 34b respectively receive light beam 134a and 134b from element 32 and resize them in the other dimension, preferably, by the same extent as the resizing performed by element 32 so as to preserve the aspect ratio.
  • Device 30 thus provides two output light beams 136a (produced by element 34a) and 136b (produced by element 34b), each independently being resized in two dimensions relative to input light beam 132.
  • optical resizing element 34 receives (expanded) light beam 134 from element 32 and transmits it to more than one direction.
  • element 34 bifurcates the light and produces two light beam 136a and 136b propagating in two opposite directions.
  • element 34 can be optically fed by a plurality of optical resizing elements, each transmitting to element 34 a different light beam originated from a different light source.
  • a representative example of this embodiment is schematically illustrated in Figure 13c, where there are two light sources (138a and 138b) transmitting light beams 132a and 132b to two optical resizing elements 32a and 32b which respectively resize the beams in one dimension to produce light beams 134a and 134b.
  • Element 34 receives light beams 134a and 134b from elements 32a and
  • device 30 comprises one or more additional optical elements 142 for performing various optical operations and/or to ease the manufacturing process.
  • the additional optical element(s) can be formed of a plurality of waveguides in expanding or non-expanding arrangement, depending on the desired functionality thereof.
  • additional element 142 is an image rotating element 144.
  • light beam 146 constituting an image therein, enters element 144 where the image is rotated by, say 90°, and exits element 144 as a rotated light beam 148.
  • light beam 148 enters elements 32 and 34 where it is being expanded, first in one dimension (light beam 150) then in the other dimension (light beam 152) as further detailed hereinabove.
  • Image rotating element 144 is particularly useful in the embodiments in which the optical resizing elements are manufactured such that their small facet and large facet are substantially orthogonal to each other.
  • Figure 15 is a schematic illustration of a layer (e.g., layer 14) of the optical resizing element in a preferred embodiment in which the layer comprises a polarizer 154.
  • Polarizer 154 can be formed, for example, by depositing metal or alloy (e.g., Cr, Au, Al, etc.) at gaps 156 between waveguides 16 so as to attenuate the transverse polarization mode.
  • the waveguides are made narrower at the region of the polarizer for efficiently stripping the transverse polarization modes.
  • the use of optical resizing elements with polarizer 154 can allow the use of input light source which produces unpolarized light, or it may improve the state of polarization of polarized light beams.
  • the coupling between device 30 and the light source can be by direct contact, or, alternatively, via one or more additional optical elements, such as, but not limited to, an arrangement of microlenses or diffractive optical elements.
  • Figures 16a-b are schematic illustrations of the coupling between device 30 and a light source, in the preferred embodiment in which the light source is an image source.
  • Shown in Figure 16a are several waveguides 16 of device 30, an image source 160 and a coupler 162 for providing optical coupling between device 30 and image source 160.
  • image source 160 is an LCD micro-display.
  • Coupler 162 preferably comprises a microlens array 164 and a polarizer 166.
  • the use of microlens array 164 is advantageous because, typically, an LCD panel includes, on the output side, a polarizer and an LCD protective glass, and the microlens array provides better coupling efficiency.
  • microlens array can be manufactured using any way known in the art, for example, as disclosed in U.S. Patent No. 5,508,834 and U.S. Patent Application No. 20040100700.
  • microlens array 164 can also be placed on the input optical element, such that each waveguide core is capped with one microlens, see, e.g., core 161 and microlens 168 in Figure 16b. This can be done by etching the input facet of the optical resizing element with an etcher that etches the cladding 163 of waveguide 16 faster than core 161.
  • the coupling can be carried out without the microlens array, e.g., by direct contact.
  • the overall thickness of the polarizer and protective glass is about 20 ⁇ m or less, and the waveguides of the optical resizing element which couples to the LCD panel have a sufficiently small numerical aperture (say, about 0.25 or less). In such configuration the cross talks between neighbor pixels, which can blur the picture, can be minimized.
  • FIG 17 is a schematic illustration of a preferred embodiment in which an input image is focused on device 30 using a lens 176.
  • a pre- magnification can be also obtained, thus relieving the required aspect ratio of the waveguides or eliminating the need for two stages magnifications as further detailed hereinunder.
  • This configuration is particularly useful with reflecting liquid crystal micro-displays, such as, but not limited to, LCD on Silicon (LCOS) or other input panels, such as, but not limited to, Digital Light Processor (DLP).
  • Shown in Figure 17 are a reflective liquid crystal micro-display 170, an external light source 172 and device 30.
  • Light 174 from light source 172 is focused by a lens 175 on micro-display 170, which reflects the light.
  • the reflected light constitutes an image therein is focused by another lens 176 on device 30.
  • a pre-magnification can be carried out also only in one dimension. Combining a distorted input (magnified in one dimension) with an optical resizing element can result in a compact thin device since in this case there is no need for two optical resizing elements in device 30, and the pre-magnification element (which can be a lens) is thin.
  • Figures 18a-b are schematic illustrations of the coupling between device 30 and a light source, in the preferred embodiment in which the coupling is by a fiber bundle.
  • one ( Figure 18a) or more ( Figure 18b) fiber bundles 180 guide the light directly to the receiving optical resizing element of device 30.
  • the fiber bundle(s) are preferably composed of many fibers with small cores to enable transmission of high resolution images. Denoting the number of rows and the number of columns in the fiber bundle by Xi and X 2 , respectively, the total number of fibers in the fibers is XiXX 2 .
  • Xj and X 2 include, without limitation, from about 500 to about 2000.
  • Xi X 2 .
  • the diameter of the core of the fibers is preferably less than 20 ⁇ m, more preferably less than 15 ⁇ m, say about 10 ⁇ m.
  • each bundle transmits one optical channel.
  • the input fiber bundle 180 is separated to four fiber bundles (180a, 180b, 180c and 18Od) which respectively feed four input facets (182a, 182b, 182c and 182d) of device 30.
  • Device 30 can also receive optical input in the form of one or more coherent light beams, e.g., a laser beam.
  • a color image can be created from a plurality (e.g., three or more) of monochromatic laser devices, for example, red, green and blue laser devices which are scanned to form a picture. Such image can be projected on the input facet of device 30 which has a small cross-section.
  • the advantages of using laser light are high brightness and the ability to calibrate the laser light spot intensity and location according to the transparency and location of the waveguides in device 30. Preferred transparency optimization procedures in accordance with various exemplary embodiments of the present invention are provided hereinunder in the Examples section that follows.
  • the light can emitted from device 30 at any predetermined angle with respect to the emitting facet.
  • the predetermined angle can be about 90°, in which case the waveguides are formed in substantially orthogonal relation to the output facet, or any other angle in which case the waveguides are tilted with respect to the output facet.
  • FIG 19 is a schematic illustration of one layer of one optical resizing element of device 30 in a preferred embodiment in which waveguides 16 are tilted with respect to the layer's end.
  • the resulting optical resizing element emits light 194 are an angle ⁇ (designated by numeral 190 in Figure 19) with respect to the output facet.
  • device 30 is designed and constructed to provide three-dimensional images.
  • the three-dimensional images can be obtained by generating two different images, of two different polarizations or two different colors. The user can then view the images using a binocular device having a different polarization or a different color for each eye, hence mimicking a three-dimensional perception of the image.
  • device 30 can function as an autostereoscopic display, whereby it is not necessary for the viewer to wear special viewing implement to keep the two images separated.
  • the autostereoscopic is provided to the user in the form of two different images which are directed to the left and right eyes of the user.
  • a representative example of an autostereoscopic display, according to various exemplary embodiments of the present invention is provided hereinunder (see Figures 34a-35c and the accompanying description).
  • Display devices are typically manufactured under a constraint of "pixel to pixel" alignment between optical coupled display panels. Specifically, for a display device to function properly, it is required to align the pixels of optical coupled panels with tolerance of microns or sub-micron. It is recognized that this requirement complicates the manufacturing process and oftentimes completely disable product manufacturability. In the present embodiments, there is no need for pixel to pixel alignment between the input picture image and element 32 or between element 32 and element 34.
  • the numbers of pixels in the picture image can be different from the number of pixels in element 32 which in turn can be different from the number of pixels in element 34.
  • the number of pixels (waveguides) in the accepting element is preferably k times larger than the number of pixels (waveguide) in the transmitting element, where A: is a number larger than I, e.g., about 2 more preferably about 3.
  • A is a number larger than I, e.g., about 2 more preferably about 3.
  • misalignment of x microns between layers is translated to an effective misalignment (at the output) of x(M- ⁇ ) for the case in which the small and large facet are opposite and parallel, xM for the case in which the small and large facet are substantially orthogonal, and x(M+ ⁇ ) for the case in which the small and large facet are coplanar.
  • the layers can be stacked at the input waveguide region within about 20 microns accuracy.
  • the alignment requirements are only in one dimension. In the embodiments in which the small and large facets are parallel (opposite or coplanar), there are no alignment requirement in the transverse direction.
  • the tolerance at the transverse direction is about x microns.
  • Misalignments of x microns due to lack of planarization in the transmitting optical resizing element (e.g., element 32) are translated to a misalignment of xM microns (where M is the magnification of the receiving element) at the output.
  • Rotation misalignment between the two optical resizing elements is preferably minimized so as to reduce image distortion.
  • Variations in the thickness and the width of the waveguides which lead to difference in the transparency of the waveguides can be added to the total loss budget of the waveguides. Preferably, some width and thickness variation can be introduced so as to suppress the Moire fringe effects.
  • FIG. 20 is a schematic illustration of an optical resizing device 200, in accordance with various exemplary embodiments of the invention.
  • device 200 can provide two-dimensional optical resizing of light.
  • Device comprises a plurality of layers 202 forming a substrate 204 having a first facet 206 and a second facet 208.
  • Layers 202 are arranged in a partially overlapping optical arrangement.
  • partially overlapping optical arrangement of layers refers to an arrangement in which each layer includes at least one region which is optically exposed at the surface of the layer.
  • An optically exposed region refers to a region capable of establishing optical communication with the environment.
  • optically exposed region can therefore emit light directed outwardly from the surface of the layer, without being substantially absorbed, reflected or scattered from adjacent layers.
  • the optically exposed regions can either emit light directed outwardly from or receive light directed inwardly to the surface of the layers, without being substantially absorbed, reflected or scattered from adjacent layers.
  • Figures 21a-b schematically illustrate a side view of two partially overlapping optical arrangements, according to various exemplary embodiments of the present invention.
  • layers 202 each having a surface 290 and an end 292.
  • Waveguides 16 are embedded in layers 202 and extending, in each layer, from a first region 293 to a second region 294 of the layer. Second regions 294 are optically exposed.
  • Second regions 294 are optically exposed.
  • light 291 propagating within layers 202 (through waveguides 16) is allowed to exit layer 202 through surface 290 and into environment 298.
  • regions 294 are physically exposed to the environment, thus establishing optical path 296.
  • regions 294 there is an overlap between adjacent layers at regions 294, such that optical path 296 passes through the layers.
  • layers 202 (or at least a portion of each layer) are manufactured from a material which enables transmission of visible light therethrough, so as to preserve optical path 296.
  • the light can be coupled out of the layers through surface 290 irrespectively whether the layers are terminated at the optically exposed regions (as exemplified in Figure 21a) or extend beyond them ( Figure 21b). Preferred configurations for coupling the light out of the layers according to various exemplary embodiments of the present invention are provided hereinunder.
  • facet 208 of device 200 is defined by the optically exposed regions of the layers. Facet 208 can be slanted or it can have a two-dimensional stepped shape (a terrace). Each layer has an expanding arrangement of waveguides defined by a circumferential boundary as further detailed hereinabove, see e.g., circumferential boundary 22 in Figures 4b, 4e, 4f and 10a. Similarly to element 10 and device 30 above, a portion or all the waveguides 16 in each layer can be tapered or partially tapered, as desired.
  • the expanding arrangement of the waveguides 16 can be achieved by waveguide bends and/or comer mirrors, whereby waveguide bends are favored from the standpoint of optical losses while corner mirrors are favored from the standpoint of device thickness, as further detailed hereinabove.
  • the expanding arrangement of the waveguides in each layer of device 200 results in optical resizing in one dimension shown by arrow 210 in Figure 20, and the partially overlapping optical arrangement of the layers at facet 208 results in optical resizing in another dimension shown by arrow 212.
  • first facet 206 is defined by ends 216 of overlapping regions 218 of layers 202.
  • Figures 21c-d schematically illustrate one (Figure 21c) and several (Figure 2Id) layers of device 200, better showing end 216 of non exposed region 218.
  • the exposed regions of layers 202 which form facet 208 are designated in Figures 21c-d by numeral 220.
  • layers 202 are partially exposed at both first 206 and second 208 facets.
  • facet 206 ( Figures 22a-b) is defined by exposed regions 222 ( Figure 22c) and facet 208 is defined by exposed regions 220.
  • exposed regions 222 Figure 22c
  • exposed regions 220 exposed regions 220.
  • Figure 22d is a schematic illustration of device 200 in a preferred embodiment in which device 200 comprises two optical resizing elements 232 and 234, where element 232 provides optical resizing in one dimension (designated by arrow 212) and element 234 receives the partially resized light and resizes it the other dimension (arrow 210).
  • element 232 is smaller in size than element 234.
  • Elements 232 and 234 can be manufactured in separate manufacturing processes and be optically coupled thereafter, or more preferably, they can be integrated element in which case their optical coupling can be achieved during the manufacturing process.
  • each layer of device 200 has two portions 432 and 434 (not shown, see Figure 22e-f), portion 432 is designated for element 232 and portion 434 is designated to element 234.
  • This embodiment is better illustrated in Figures 22e-f showing top view of one layer ( Figure 22e) and several layers (Figure 22f) stacked one over the other in a partial overlapping optical arrangement.
  • the waveguides extend from a first region 18 to a second region 20, thereby forming a longitudinally expanding arrangement, as further detailed hereinabove.
  • first 432 and second 434 portion which, as stated are designated for elements 232 and 234, respectively.
  • each of elements 232 and 234 can be independently manufactured layerwise or as a bulk, as further detailed hereinunder (see Figures 26-27h and accompanying description.
  • element 232 serves as the transmitting element within device 200 whereby light entering element 232 through facet 236 is transmitted by element 232 through facet 238 which is located at the interface between elements 232 and 234.
  • element 234 serves as the receiving element within device 200 whereby the light transmitted by element 232 is received by element 234 through facet 240, also located at the interface between the devices. After being resized in dimension 210 the light exits element 234 through facet 242.
  • FIG. 234 is manufactured according to the principle of partially overlapping optical arrangement, as further detailed hereinabove, whereby the exposed portions of its layers form facet 242. Similarly to facet 208 above, facet 242 can be slated or it can have a terrace shape. Also illustrated in Figure 22d is an expanding structure 224 which according to a preferred embodiment of the present invention is optically coupled to facet 242. Expanding structure 224 serves for expanding light rays passing therethrough, as further detailed hereinunder.
  • the expanding arrangement of the waveguides in element 232 results in optical resizing in dimension 212
  • the terrace or slanted shape of facet 242 of element 234 results in optical resizing in dimension 210.
  • the cladding layers of device 200 can be made of an absorbing or non- absorbing material, as desired.
  • the advantage of using absorbing material is that it improves the contrast
  • the advantage of using a transparent material is that it allows the manufacturing of a transparent display which does not block the scene behind it.
  • polarizers can be added between the waveguides cores, as further detailed hereinabove (see Figure 15).
  • the coupling of light out of the partially overlapping optical arrangement of the present invention can be achieved in more than one way.
  • the light is coupled out of facet 208 using an arrangement of reflecting elements.
  • the light propagates through the waveguides substantially in parallel to the surface of the layer until it impinges on the reflecting elements which redirect the light outwards through the surface.
  • the light is coupled out of facet 208 using an arrangement of transmitting elements (typically waveguides).
  • an arrangement of transmitting elements typically waveguides.
  • a combination of reflecting and transmitting elements are also contemplated. The embodiment in which the light is coupled out via an arrangement of reflecting elements. The embodiment in which the light is coupled out via an arrangement of reflecting elements is described hereinbelow, and the embodiments in which the light is coupled out via an arrangement of transmuting elements or a combination of reflecting and transmitting elements are described hereinafter (see Figures 26-27h).
  • Figures 23a-b are schematic illustrations of a side view ( Figure 23a) and a top view ( Figure 23b) of a portion of facet 208 of device 200 in a preferred embodiment in which facet 208 has a two-dimensional stepped shape (a terrace).
  • Figures 23c-d are schematic illustrations of a mirror 282 placed in the layers of device 200, according to the presently preferred embodiment of the invention.
  • a few mirrors 282 (e.g., total internal reflection mirrors) with different reflection coefficients are preferably placed in a reflection region 283 of each layer 202 of device 200.
  • Mirrors 282 collect light propagating in the layers and redirect it so as to couple the light out of facet 208.
  • the propagating light and redirected light are designated in Figures 23a-b by numerals 284 and 286, respectively.
  • Mirrors 282 are preferably wide, so as to optimize the collection and coupling of the light.
  • the different reflection coefficients of mirrors 282 can be realized by providing mirrors of different heights.
  • mirrors 282 can be narrow, without variations of reflection coefficients such that light striking the mirrors is fully reflected.
  • mirrors 282 are disposed substantially homogenously across reflection region 283 to facilitate efficient collection of light 284.
  • Such configuration results in a substantially homogenous reflection of light out of facet 208.
  • redirected light 286 can be further expanded in two dimension upon striking the boundary between facet 284 and the external medium. Such expansion typically occurs when facet 284 is coated by a protective coat, such as, but not limited to, a glass or a polymer or when the light is coupled downside as illustrated in Fig. 33b.
  • the redirected light before and after being expanded on the protective coat is illustrated in Figure 23b by squares 286 and circles 288, respectively. Still alternatively, both methods can be combined, for example, by placing narrow partially reflecting mirrors across the terrace surface.
  • the mirrors can be fabricated in polymer waveguides, e.g, by molding or ablation process.
  • mirrors 282 can have a planar ( Figure 23 c) or non-planar ( Figure 23d) shape.
  • Flat mirrors are preferred in applications in which a narrow or moderate field-of-view is required and can be obtained, for example, using a series of laser ablation pulses.
  • Non-planar mirrors are preferred in applications in which the required field-of-view is wide, and can be obtained, for example, using fewer (e.g., one) laser ablation pulse.
  • Figures 24a-e are schematic illustrations of a side view of optical resizing element 234, according to various exemplary embodiments of the present invention.
  • Layers 202 of element 234 serve for two purposes: (i) coupling the light out of element 234, and (ii) facilitating the optical resizing (expansion, in the present example) in dimension 210.
  • the propagating light and the outgoing light are designated in Figures 24a-e by numerals 246 and 247, respectively.
  • Also shown in Figures 24a-e is the typical pixel size characterizing outgoing light 247.
  • layers 202 comprises mirrors 248 positioned on the terminals the waveguide so as to redirect light rays 246 propagating therethrough.
  • Mirrors 248 can be 45° mirrors - total internal reflection (TIR) mirrors, full or partially reflective mirrors and they can have a planar or non- planar shape, as further detailed hereinabove. Additionally, the mirrors can be coated with a high reflecting material.
  • Figure 24a illustrates the preferred embodiment in which 45° mirrors are used and Figure 24b illustrates the preferred embodiment in which TIR mirrors are used.
  • grooves 250 are formed in layers 202 so as to force total internal reflection hence redirection of light out of the layers.
  • element 234 comprises a Bragg reflector 261 which redirects the light rays out of light out of element 234.
  • element 234 comprises a holographic optical element 263, designed and constructed the redirect the light rays out of light out of element 234.
  • Element 234 can be manufactured as a part of element 232, in which case the layers forming the elements are made of a single substrate, using, for example, a photomask of the type shown in Figure 21c above. More preferably, each layer can be processed using a different mask so as to reduce potential vertical coupling. Such manufacturing process also reduces the length of the waveguides, whereby a single diagonal path can be utilized (rather than two perpendicular paths).
  • the layers can be fabricated to their exact length and then stacked to form facet 242, or they can be first stacked to form the facet 242 and then polished or cut thereafter to form facet 236.
  • Element 234 can also be manufactured as a separate unit, for example by stacking layers with substantially parallel waveguides one over the other, to form a partially overlapping optical arrangement in which facet 242 has a slanted or terrace shape.
  • the layers of device 200 are made of polymeric material, more preferably a flexible polymeric material, to facilitate flexibility of device 200. Furthermore, the layers of device 200 can be attached to each other on one side (e.g., the input side) while allowing their other sides (e.g., the output side) to be detached. With such configuration, device 200 can be made foldable.
  • a representative example of a foldable device is illustrated in Figure 25, showing device 200 in which layers 202 are attached on their input side 251 and allowed to be detached on their output side 255.
  • device 200 is manufactured as two separate elements 232 and 234 which are coupled thereafter, it can be made foldable by fully attaching the layers of element 232 and partially attaching the layers of element 234.
  • an optical resizing element 110 has a first 112 and a second facet 114, where facet 114 is slanted at an angle ⁇ hence being larger than facet 112.
  • Element 110 has a plurality of waveguides 16 extending from facet 112 and bended towards facet 114, thus providing optical resizing along direction 115.
  • waveguides 16 arrive at facet 114 at an angle ⁇ , conveniently defined relative to the normal 116 to the facet, ⁇ can have any value which allows the optical communication between element 110 and the environment and provide optical resizing. Generally, optical communication and optical resizing can be achieved whenever with the environment for any value of ⁇ which is lower than some angle ⁇ c . Preferable, ⁇ is approximately zero, in which case waveguides 16 arrive to facet 114 approximately perpendicularly.
  • Bended waveguides can be manufactured, e.g., according to the principles of element 10 above.
  • layers of trapezoidal or similar shape can be stacked one onto the other, such that their surfaces 117 substantially overlap, and their ends 119 form slanted facet 114. Light thus propagates within the layers (through the waveguides) and exits the layer through end 119.
  • Element 110 can be optically coupled to any of the above optical resizing elements such as to provide optical resizing in two dimensions.
  • element 110 can replace element 34 of device 30 or element 234 of device 200.
  • Figures 27a-b schematically illustrates another preferred manufacturing process of element 234.
  • element 234 is processed by stacking alternating sheets of high index material and low index material to form a stack 231 before the formation of waveguides 233 therein. Subsequently, a slant cut is performed in stack 231 to form slanted facet 242. Once facet 242 is prepared individual waveguides 233 are formed in stack 231 by etching grooves 235 therethrough. To avoid too deep etching, the process can be executed in batches of, say, tens or hundreds of layers, whereby the grooves are etched batch by batch.
  • the manufacturing process preferably includes four steps, in which in a first step batches of stacked layers are prepared, in a second step the batches are etched to form the grooves therein, in a third step the batches are stacked one onto the other, and in the fourth step the stack of batches is cut along a slanted line to form slanted facet 242.
  • Grooves 235 which separate between the waveguides of each layer, may be filled with a filling material whose refractive index is lower than the refractive index of the waveguides (the high index material).
  • the difference between the refraction indices of the filling material and the waveguides is preferably large ⁇ e.g., about 0.1 or more), so as to provide a wide field-of-view at the output of element 234.
  • the filling material preferably has enhanced light absorbing properties to reduce scattered light. Representative example of such material include, without limitation, is a black tone added to the low index polymer.
  • grooves 235 can remain unprocessed in which case the waveguides are separated by air.
  • Figures 27c-h are schematic illustrations of expanding structure 224, according to various exemplary embodiments of the present invention.
  • structure 224 serves for expanding the light beam passing therethrough, in addition to the optical resizing provided by element 232 or as an alternative thereto.
  • device 200 may or may not include optical resizing element 232.
  • structure 224 comprises a stack of patterned layers; in the preferred embodiment illustrated in Figure 27d structure 224 comprises a bulk of guiding material patterned and grooved; and in the preferred embodiment illustrated in Figures 27e-f, structure 224 comprises a stack of layers of banded waveguide in expanding arrangement, similarly to the construction and operation of optical resizing element 10.
  • an antireflection coat or an index matching material 254 can be added between facets 242 and structure 224.
  • the shape and materials of element 234 and structure 224 are preferably selected such that guided light is bent towards the inner side 275 of facet 242 while scattered, non-guided light, continues to propagate in its original direction impinging on inner side 275 of facet 242 at an angle which is above the critical angle for total internal reflection.
  • device 200 is less sensitive to contrast reduction due non-guided light.
  • the scattered light is not emitted from facet 242.
  • the waveguides of structure 224 have higher index of refraction compared to the waveguides of element 234. In this way the aspect ratio (cladding layer width to thickness) at element 224 can be eased.
  • Element 234, shown in Fig 27f, is composed of layers of core material and layers of cladding material. Being deposited and not etched, cladding layers which can be substantially thinner than the core layers, can be fabricated.
  • structure 224 is composed of thick layers with wide core and relatively wide cladding barrier. As too narrow cladding barriers are difficult to be fabricated in a thick layer, it is preferred to increase the width of the waveguides (and barriers).
  • the spatial and optical parameters of element 234 and structure 224 are selected so as to satisfy Snell's law.
  • Ni, N 2 are the refraction indices of the waveguides of element 234 and structure 224, respectively
  • W ⁇ , W 2 are the thickness of the layers of element 234 and the width of layers of structure 224, respectively
  • ⁇ i is the slanting angle ⁇ i of facet 242
  • ⁇ 2 is the banding angle of the waveguides of structure 224
  • Ni 1.50
  • ⁇ t 5.7°
  • N 2 1.7
  • structure 224 is preferably manufactured using the same technology.
  • the advantage of this embodiment is that it can reduce optical losses at the interface between element 234 and structure 224. Additionally, the use of the etching technology preserves a high index contrast.
  • structure 224 is fabricated and attached to stack 231 (see Figure 27a-b) before etching. Thereafter, stack 231 and structure 224 are etched to form the grooves. Within structure 224, low spatial modes (perpendicular to the grooves) are guided between the cladding layers thereof and the high spatial modes are guided between the grooves.
  • structure 224 comprises a stack
  • the regions can be cuboids or have any other geometrical shape.
  • the lower layer of structure 224 (designated layer 258a) is an array of high index cuboids terminated by mirrors 260 (e.g., TIR mirrors) which are preferably, but not obligatorily curved for enhancing the beam divergence with structure 224.
  • Regions 252 of the other layers 258 of structure 224 are preferably larger than regions 252 of layer 258a for reducing alignment tolerance requirements.
  • the space between element 234 and structure 224 is preferably filled with low refractive index filling material for reducing back reflections and beam divergence.
  • the space between the regions 252 can be filled with absorbing black material to reduce scattered light and improve display contrast.
  • Optical coupling between element 234 and structure 224 can also be effected by providing waveguides with slanted ends within element 234 (see Figure 27h).
  • Figures 28a-c are schematic illustrations of a top view ( Figures 28a-b) and a side view ( Figure 28c) of layers of device 200 in a preferred embodiment in which the layers are low-weight layers.
  • Figure 28a is a top view of layer 202 of one optical resizing element (element 232, element 234 or both elements 232 and 234 in the embodiment in which they have common layers).
  • waveguides 16 are only partially tapered at their end 262, while along most of their length the cross section remains substantially unchanged.
  • waveguides 16 are coated with a thin layer 264 of lower index cladding material (not shown, see Figure 28c) and the reminding space can be left substantially empty.
  • supporting members 260 are preferably placed between waveguides 16, so as to maintain the planar shape of each layer and prevent collapsing of layers.
  • Supporting members 260 can be made of short section waveguides which are fabricated in parallel with the entire waveguides.
  • Members 260 can have any geometrical shape (e.g., a cuboid).
  • Figure 28b is a top view of layer 258 of expanding structure 224.
  • the high refractive index regions 252 of structure 224 can be spaced apart so as to reduce the weight of each layer of structure 224.
  • Supporting members 260 can be placed between regions 252 to maintain the planar shape of each layer of structure 224 and prevent collapsing,
  • Figure 28c is a side view of layers 202 or 258, showing members 260 positioned between adjacent light transmitting elements (waveguides 16 or high refractive index regions 252). Also shown in Figure 28c is the preferred construction of each individual layers in which the light transmitting elements are formed on a bottom cladding layer 266 and coated by a top cladding layer 264.
  • Another way to reduce the overall weight of device 200 is to minimize the empty areas on each layer by manufacturing layers in the shape of the circumferential boundary 22, as shown in Figure 21c above.
  • FIGS 29a-e are schematic illustrations of a preferred folding technique for manufacturing device 200, according to various exemplary embodiments of the present invention.
  • the folding technique is advantageous in applications in which it is preferred to manufacture rectangular layers, e.g., to facilitate mass production of the layers.
  • the folding technique can be employed both for manufacturing any part of device 200.
  • the folding technique can be employed for manufacturing elements which provide optical resizing in one dimension or two dimensions.
  • the folding technique is employed for manufacturing optical element which provides optical resizing in two-dimensions, whereby the expanding arrangement of waveguides in each layer provides the optical resizing in the first dimension and the partially overlapping optical arrangement provides the optical resizing in the second dimension.
  • the layers of device 200 are preferably formed of a flexible polymer. Additionally, the layers are preferably made sufficiently thin to allow their folding. Once a rectangular layer is formed it is being folded to form a predetermined angle of about 90° (with a radius of curvature allowed by the polymer waveguides so as not to increase the bend loss).
  • the folded layer thus comprises an expanding arrangement of waveguides, whereby the input region is smaller than the output region.
  • a representative example of a folded layer 270 with an input region 273 and an output region 271 is illustrated in Figure 29a, and selected steps of the manufacturing process are illustrated in Figures 29a-d.
  • FIG. 29a-d Shown in Figure 29a-d are a folded layer 270 (Figure 29a) having input waveguides 280 and output waveguides 276, and an additional layer 272 (Figure 29b) which is added to folded layer 270, in a manner such that the output waveguides 274 of layer 272 are aligned to the output waveguides 276 of layer 270 ( Figure 29c).
  • Layer 272 is then folded ( Figure 29d) such that the input waveguides 278 of layer 272 are aligned with the input waveguides 280 of layer 270.
  • a top view of the resulting partially overlapping arrangement of layers is schematically illustrated in Figure 29e, showing exposed regions 220 and overlapping regions 218.
  • the above fabrication process can also be carried out in a reverse order.
  • the input waveguides 280 of layer 270 are aligned first and the output waveguides 274 of layer 272 are aligned thereafter.
  • Figures 30a-b are schematic illustrations of a simultaneous process for manufacturing four optical resizing elements, in various exemplary embodiments of the invention.
  • Figure 30a illustrates a top view of layers 300 which can be used to form four optical elements. Once layers 300 are prepared, they are stacked and cut along vertical path 306 to form two stacks 302 of layers (see Figure 30b). Subsequently stack 302 can be cut along a slanted path 304.
  • Figure 31 is a schematic illustration of device
  • device 200 in a preferred embodiment in which device 200 receives light from a plurality of sources.
  • device 200 receives optical input from four light sources (not shown).
  • Device 200 comprises two optical resizing elements, designated 132a and 132b, both serving as transmitting elements within device 200, and one optical resizing element, designated 134 serving as receiving element within device 200.
  • Element 134 comprises a slanted or terrace facet 242 and is optically coupled to both elements 132a and 132b.
  • the principles and operations of elements 132a and 132b are similar to the principles and operations of elements 32a and 32b above, mutatis mutandis the coupling to slanted element 134.
  • FIGS 32a-b are schematic illustration of a top view ( Figure 32a) and a cross sectional view ( Figure 32b) of device 200 in a preferred embodiment in which device 200 receives optical input in the form of a plurality (e.g., two or more) of monochromatic light sources and uses the optical input to produce a resized chromatic light beam.
  • Figure 32b is a cross sectional view along the cut AA' in Figure 32a.
  • Device 200 can be used, for example, to provide a magnified chromatic image using a plurality of monochromatic images, as further detailed hereinabove.
  • device 200 comprises a plurality of layers 320 in a partially overlapping optical arrangement forming three input facets 326a, 326b and 326c, and one output facet 328 having a slanted or terrace shape, as further detailed hereinabove.
  • Layers 320 can be manufactured using the folding technique or using any other of the aforementioned technique. It is to be understood that although Figures 32a-b describes the embodiment in which a single element (the waveguides stack) provides two-dimensional optical resizing, it is not intended to exclude the embodiment in which two optical elements are used, (e.g., elements 132 and 134, above).
  • three monochromatic optical inputs 322 are transmitted from three monochromatic image sources (not shown) to device 200.
  • Layers 320 of device 200 are preferably arranged in an alternating sequence, whereby the waveguides of each layer are optimized according to the average wavelength of one monochromatic input.
  • a first type of layers 320a is optimized for red light
  • a second type of layers 320b is optimized for green light
  • a third type of layers 320c is optimized for blue light.
  • the layers are coupled to the different monochromatic light sources in accordance with their wavelength optimization.
  • Each layer couples the light out of device 200 using mirrors 324 (e.g., TIR mirrors) or using any other way as further detailed hereinabove.
  • Mirrors can also be optimized to the average wavelength of the corresponding optical input.
  • the present embodiments are suitable for imagery optical data as well as non imagery optical data. Specifically, the present embodiments can be used to provide a chromatic image or a chromatic back illumination for another display device, as further detailed hereinabove.
  • the layers of device 200 are better shown in Figures 33a-c which schematically illustrate the coupling of light out of the layers. Shown in Figures 33a-c are layers 331, arranged in a partially overlapping optical arrangement. Each layer end with a mirror 333, preferably a TIR mirror, such that light 335 propagating within layers 331 is being redirected by mirrors 333 and coupled out of the layers.
  • light 335 can exit through the free side 337 of the layer's reflection region 345 (see Figure 33 a) or through a side 339 of reflection region 345 which is engaged by adjacent layers (see Figure 33b-c).
  • the embodiment illustrated in Figure 33a is referred to herein as a forward light coupling and embodiment illustrated in Figure 33b is referred to herein as a backward light coupling.
  • Backward light coupling is preferred in configurations in which the layers have substantial uniform thickness and the overall thickness of the layers at the emitting region of device 200 is small (typically, without limitation, lower than 10 mm, e.g., about 2 mm).
  • the advantage of the backward light coupling is in its simpler fabrication process and in its simple depositing of (high reflection) coating on the mirrors.
  • the mirrors can be produced during or after the production of the waveguides, or they can be produced in a single step once several or all the layers are laminated.
  • device 200 comprises a light transmissive plate 341 disposed in a slanted orientation over layers 331. Additionally, the gap between layers 331 and plate 341 can be filled with an index matching material 343 such that light 335 is coupled out of device 200 substantially perpendicularly to plate 341. Plate 341 is particularly useful in the backward light coupling embodiment in which roughness of the back surface can deteriorate the light out-coupling.
  • Devices 200 and 30 can also be used to provide three-dimensional images, by generating two different images, of two different polarizations or two different colors, as further detailed hereinabove.
  • device 200 can be constructed similarly to Figure 32, with two optical inputs at two different polarizations (instead of different colors). The user can then view the images using a binocular device having a different polarization for each eye.
  • devices 200 and 30 can function as an autostereoscopic display. This can be done in more than one way, as further detailed hereinbelow with reference to Figures 34a-d and 35a-c.
  • device 200 is manufactured with two input facets, 330 and 332 each receives a different image, designed to be viewed by the left eye and the right eye of the user.
  • the layers of device 200 can be arranged such that the optical information arriving to input 330 is directed to the left eye and the optical information arriving to input 332 is directed to the right eye. This can be done by an appropriate orientation of the mirrors 334 of the different layers to focus the output beam to a single spot 336, also known as the "sweet spot" of the autostereoscopic image (see Figure 34c).
  • the user can then view a three-dimensional image by placing the left eye in the left part 344 of the sweet spot and the right eye in the right part 342 of the sweet spot.
  • the focusing of the output beam to spot 336 can be achieved by bending output facet 338, as shown in Figure 34d.
  • the sweet spot position can be varied by varying the curvature of facet 338.
  • the layers of device 200 can be arranged such that the waveguides 16 have an appropriate orientation to focus the output beam to spot 336.
  • the advantage of this embodiment is that the beam orientation is governed by the waveguide orientation and not by the mirror facet angle. Fabrication of waveguides with controlled orientation is much simpler than fabrication of mirrors with controlled facet angle. In another preferred embodiment the waveguides orientation is the same but the mirror orientation is altered in order to reflect the beams to the desired direction.
  • Figure 36 schematically illustrates different optical regions in the field-of-view of device 200, in the preferred embodiment in which devices 200 provides two optical outputs, a "left" output 346 and a "right” output 348.
  • the field- of-view generally includes four optical regions.
  • Regions 352 and 354 can be resized (reduced or enlarged) as desired by controlling the width of the output field.
  • Figures 37a-b are schematic illustrations of one layer ( Figure 37a) and the resulting field-of-view ( Figure 37b) in the preferred embodiment in which device 200 provides a plurality of autostereoscopic images.
  • the end portion 360 of each waveguide 16 designated to emit light through the output facet splits into a plurality of waveguides (three waveguides 362a, 362b and 362c in the present example), each being terminated by a separate mirror (in the present example mirrors 364a, 364b and 364c).
  • the waveguides are oriented to focus the respective portion of light onto different sweet spots (spots 366a, 366b and 366c in the present example).
  • the present embodiment can also be employed to provide a plurality of two-dimensional images, to a plurality of directions.
  • device 200 when device 200 is implemented in a display device, users observing the display from different directions can view different images.
  • the coupling can be done utilizing a coupler, e.g., a microlens array with or without a polarizer, as further detailed hereinabove (see Figure 16a).
  • a coupler e.g., a microlens array with or without a polarizer
  • device 200 can function without a coupler or using a microlens array which is placed or formed on the input optical element, as further detailed hereinabove (see Figure 16b).
  • an input image can be focused on device 200 using a lens or another focusing element as further detailed hereinabove and illustrated in Figure 17.
  • the coupling between device 200 and the light source is via one or more fiber bundles, as further detailed hereinabove (see Figures 18a-b).
  • Device 200 can also receive optical input in the form of a laser beam which can be projected on the input facet of device 200.
  • the transparency of device is affected by few loss mechanisms: (i) propagation loss within the device; (ii) bend and tapering loss within the device; (iii) coupling loss between the optical elements of the device; and (iv) reflection losses at the interfaces.
  • the waveguides are polymeric waveguides, more preferably PMMA waveguides or d-PFMA waveguides.
  • the bend loss in various exemplary embodiments of the invention is due to interaction of light with corner mirror.
  • a corner loss of 1.2 dB was reported for the 50x50 ⁇ m multimode polymer waveguide with air-cladding mirror [J-S Kim and J-J Kim, "Stacked polymeric multimode waveguide arrays for two-dimensional optical interconnects," J. Lightwave Tech, vol 22, 840-844, 2004].
  • Lower losses, below 0.5 dB, are also achievable [Ahmad, "Ultracompact corner-mirrors and T-branches in silicon-on-insulator,” IEEE Photon. Tech. Lett., vol. 14, 65-67, 2002].
  • the losses can be lower than 0.1 dB.
  • the tapering loss is negligible.
  • the typical tapering loss depends on the mode structure of the input beam and the taper length; for a fundamental input mode and a few mm long taper the loss can be below 0.1 dB.
  • the tapering can be stepped, while for contraction uses, a smooth tapering is preferred so as to minimize loss.
  • the extent of coupling loss at the interface between the input light source and the device depends on the optical arrangement used to facilitate the coupling, the ratio of core to cladding in the waveguide and the ratio of width to gap of the pixels (in the extent that there is no focusing element like etched lenses at the facet).
  • the filling factor is higher than the filling factor in case of waveguides with round cross section.
  • the extent of coupling loss between the optical elements of the device can be negligibly low by a judicious selection of the numerical aperture of the waveguides.
  • the numerical aperture of the receiving optical resizing element e.g., element 34
  • the numerical aperture of the emitting optical resizing element e.g., element 32).
  • Reflection between the input light source and device 30 can be negligibly low by placing index matching adhesive between device 30 and the optical arrangement which couples the light source to device 30.
  • the reflection at the large facet of the second optical resizing element is given by ( «-l) 2 /( «+l) 2 where n is the refractive index of the core. This facet can be coated with antireflection coating to further reduce the reflection.
  • the device contrast ratio is only slightly affected by the propagation loss since the lost scattered light propagates substantially parallel to the large facet of device 30. Nevertheless, light lost at the coupling between the interfaces and light scattered at the bends can reduce the contrast ratio, in particular in the embodiments in which regions 18 and 20 of the layers are parallel and located on opposite sides of the layer.
  • Optical losses due to waveguides non-homogenous propagation loss can be reduced or substantially eliminated (e.g., reduced to less than 20 %, more preferably less than 10 %, say about 5 % or less of its former value) by illuminating the input image in a non homogenous way.
  • the input image 380 can be distorted such that there is a brightness gradient 382 across the length and width of the image so as to compensate the differential waveguide losses.
  • Figure 39a is a schematic illustration of a layer (e.g., layer 14) of the optical resizing element in a preferred embodiment in which the layer comprises light absorbers 370 selected so as to improve the contrast ratio of the light propagating within waveguides 16.
  • Light absorbers 370 can be deposited across layer 14 or in small areas within layer 14. The light absorbers can be black tone added to the cladding material. In the embodiments in which regions 18 and 20 are collinear or on adjacent sides of layer 14 the effect of reduced contrast ratio is less pronounced and the skilled artisan may prefer not to include light absorbers 370. Yet, the use of light absorbers in these embodiments is also contemplated.
  • An alternative way to improve contrast ratio is to use a slightly absorbing cladding layer between the waveguides.
  • a cladding layer with absorption coefficient of about 1 dB/cm can absorb all or most of the scattered light while adding less than 0.01 dB/cm to the waveguide loss.
  • the output light beam can have non uniform brightness.
  • parasitic losses can be added to the shorter waveguides. This can be done, in more than one way. In one embodiment, the parasitic losses are added by reducing the waveguide width, in another embodiment the parasitic losses are added by reducing bend radius, and in an additional embodiment the parasitic losses are created by adding bends or parasitic intersected waveguides to the layers.
  • the coupling to the waveguides can be tailored by modifying the taper width (controlling the amount of light coupled to the waveguide) or the taper length (controlling the efficiency [transparency] of the taper).
  • the different loss of the waveguides can be compensated by assigning different cross sections to the waveguides.
  • Figure 39b schematically illustrates an embodiment in which the longer waveguides of the layer have wider cross-sections such that more light is coupled to the wider waveguides to overcome their higher loss (due to their longer length).
  • the waveguides are tapered towards the output panel, in order to obtain equal width there.
  • Non tapered waveguides are also contemplated.
  • the 90° waveguide bends can also be replaced with smooth bends.
  • the waveguides can have different length not only in the layer but also between the layers.
  • the waveguides in the upper layer are shorter than the waveguides in the underneath layer. Equal transparency for waveguides in different layers can be achieved by assigning different waveguide width for each layer.
  • the thickness of the (core) waveguides in a layer can be altered in order to compensate for the layers different waveguides' length. In this embodiment the waveguides in the upper layers are thinner than the waveguides in the lower layers.
  • device 30 is designed and constructed to provide the resized light at a predetermined field-of-view.
  • One way to achieve a predetermined field-of-view for device 30 is by a judicious selection of the waveguide parameters for the optical element from which device 30 outputs the light ⁇ e.g., element 34).
  • the refractive indices and numerical aperture (N. A.) of the waveguides are selected so as to satisfy the formula: N.A.
  • the effective field-of-view can be selected by tailoring the tapering shape, i.e. using a non-linear taper shape. In particular, different field-of-views can be obtained for different directions.
  • Different field-of-views for different directions can also be achieved by selecting a first cladding material within the layers and a second, different, cladding material between layers such that the field-of-view in the longitudinal direction (parallel to the layers) differs from the field-of-view in the transverse direction (substantially orthogonal to the layers).
  • the field-of-view of device 30 can be enlarged by adding a diffusive screen at the output facet or by etching the output facet to make it diffusive.
  • the diffusive screen can also be configured to compensate optical losses.
  • the field-of-view can be enlarged by increasing the difference An between the refraction indices of the core and cladding.
  • a high An value can be chosen for the entire optical resizing element or, alternatively, An can be increased in a gradual manner towards the output facet.
  • Gradually varying An can be achieved for example in a production process where the core is written by a direct writing UV lithography, where the core An relative to the cladding is a function of the UV exposure time.
  • the increase in refraction index come together with a diffusion mechanism such as added scattering centers in the core material or scattering by added bends to the waveguides. These scattering mechanisms convert lower order modes to higher order modes therefore utilizing the capability of the higher An waveguide to hold higher order modes. It is the higher order modes which contribute to the large field of view patterns.
  • the ability to adjust the field-of-view can significantly improve the brightness of the outpurted light.
  • Figure 40 illustrates a procedure for improving the brightness of the output light.
  • the improvement involves an efficient collection of the light 390 from the light source 392 and an adjustment of the field of view of device 30 such that there is a minimal or no brightness loss.
  • the field-of-view is reduced by the same amount as the expected reduction in brightness, such all or most (say at least 90 %) of the optical energy of light 390 is carried by output light 394.
  • FIG. 41 is a schematic illustration device 30 in a preferred embodiment in which waveguides 16 are tilted with respect to the layer's end (see, e.g., Figure 19).
  • the resulting optical resizing element emits light 394 are an angle ⁇ with respect to the output facet.
  • the present embodiment results in a modification of the field-of-view of device 30.
  • the adjustment of the field-of-view can also be employed at the interface between the optical resizing elements of device 30, for increasing the spatial modes at the receiving element.
  • the adjustment can be achieved by varying the relative orientation between the waveguides of different optical element and/or the value of An. For example, when the waveguides of the transmitting element (e.g., element 32) are not parallel to the waveguides of the receiving element ⁇ e.g., element 34), and An of the receiving element is higher than An of the transmitting element, the higher spatial modes exciting at the interface between the two elements successfully propagate within the receiving element. As a result, the field-of-view at the output facet of the device is increased. Increment of spatial modes can also be achieved within the optical resizing element (rather than on the interface between two such elements) by establishing slanted connection between two waveguides of the optical resizing element.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Couplings Of Light Guides (AREA)
  • Optical Integrated Circuits (AREA)
  • Diffracting Gratings Or Hologram Optical Elements (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
  • Light Guides In General And Applications Therefor (AREA)

Abstract

L'invention concerne un procédé de redimensionnement optique. Le dispositif comprend une pluralité de couches formant un substrat ayant une première facette et une deuxième facette. Chacune de ces couches comprend une configuration de guides d'ondes formée et/ou intégrée dans la couche. Dans un mode de réalisation, les couches sont disposées optiquement de façon à se chevaucher partiellement de sorte que chaque couche présente une zone exposée optiquement au niveau de la deuxième facette. Dans un autre mode de réalisation, le dispositif comprend deux éléments de redimensionnement optique, chaque élément étant configuré pour une expansion ou une contraction en une dimension de sorte que la lumière se propageant dans le dispositif subit un redimensionnement optique en deux dimensions.
EP05816041A 2004-12-14 2005-12-14 Dispositif et procede de redimensionnement optique Withdrawn EP1831741A2 (fr)

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US63551004P 2004-12-14 2004-12-14
PCT/IL2005/001344 WO2006064500A2 (fr) 2004-12-14 2005-12-14 Dispositif et procede de redimensionnement optique

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US10605984B2 (en) 2016-12-01 2020-03-31 Waymo Llc Array of waveguide diffusers for light detection using an aperture
US10502618B2 (en) 2016-12-03 2019-12-10 Waymo Llc Waveguide diffuser for light detection using an aperture
CN110286486B (zh) * 2018-06-03 2021-08-20 胡大文 用于输送光学图像的方法
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CN116951345B (zh) * 2023-06-07 2024-09-06 东莞市谷麦光学科技有限公司 一种匀光片和背光模组

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JP2008527399A (ja) 2008-07-24
KR20070100729A (ko) 2007-10-11
WO2006064500A3 (fr) 2006-10-05
CN101124497A (zh) 2008-02-13
WO2006064500A2 (fr) 2006-06-22

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