Abstract: The present invention is directed to wearable display technologies. More specifically, various embodiments of the present invention provide wearable augmented reality glasses incorporating projection display systems where one or more laser diodes are used as light source for illustrating images with optical delivery to the eye using transparent waveguides. In one set of embodiments, the present invention provides wearable augmented reality glasses incorporating projector systems that utilize transparent waveguides and blue and/or green laser fabricated using gallium nitride containing material. In another set of embodiments, the present invention provides wearable augmented reality glasses incorporating projection systems having digital lighting processing engines illuminated by blue and/or green laser devices with optical delivery to the eye using transparent waveguides.

Abstract: A display includes light-scattering regions. Each of the light-scattering regions is provided with linear protrusions and/or recesses having the same longitudinal direction. The light-scattering regions are different from each other in the longitudinal direction.

Abstract: A head-mounted or helmet-mounted display apparatus is provided. The apparatus includes an optical element which in use is disposed in front of the eyes of a user. The optical element comprises a waveguide portion. The apparatus further includes a first light source and a second light source of image-bearing light. The apparatus further includes first diffraction element for propagation of image-bearing light of the first light source through the optical element. The apparatus further includes a second diffraction element for propagation of image-bearing light of the second light source through the optical element. The first light source and the second light source is disposed such that relative angular movement of the first light source and the second light source about an axis of symmetry of the optical element adjusts the inter-pupillary spacing of a first visible image and a second visible image presented to a respective eye of a user.

Abstract: The present invention discloses a method for manufacturing a zero-order diffractive filter comprising a high-index material having an upper surface and a lower surface. The high-index material is positioned between a first low-index matter and a second low-index matter; the lower surface is adjacent to said first low-index matter and the upper surface is adjacent to the second low-index matter. Moreover, the high-index material has an index of refraction that is higher than the index of refraction of both said first low-index matter and said second low-index matter. The method comprises at least the following procedure: selectively providing, by employing at least one wet-coating technique, at least one of the following at least partially: the high-index material onto said first low-index matter.

Abstract: The invention concerns a film element having a replication layer (43), wherein an optically active surface structure (27) is shaped in a first surface of the replication layer. The surface structure is formed in at least a first region of the film element (35) by a first diffractive surface relief (46) comprising a plurality of successive elements following a first envelope curve (47), wherein the elements respectively comprise an element surface (48) arranged substantially parallel to a base surface and at least one flank adjoining the adjacent element surface or surfaces, the element surfaces (48) of adjacent elements are spaced in a direction perpendicular to the base plane, with a first optical spacing or a plurality of the first optical spacing, wherein the first optical spacing is between 150 nm and 800 nm, preferably between 150 nm and 400 nm.

Abstract: An optionally transferable optical system with a reduced thickness is provided. The inventive optical system is basically made up of a synthetic image presentation system in which one or more arrangements of structured image icons are substantially in contact with, but not completely embedded within, one or more arrangements of focusing elements. The focusing element and image icon arrangements cooperate to form at least one synthetic image. By way of the subject invention, the requirement for an optical spacer to provide the necessary focal distance between the focusing elements and their associated image icon(s) is removed. As a result, overall system thicknesses are reduced, suitability as a surface-applied authentication system is enabled, and tamper resistance is improved.

Abstract: A Head Up Display can be utilized to find light from an energy source. The Head Up Display includes a first waveguide having a first input coupler and a first output coupler. The Head Up Display can also include a second waveguide having a second input coupler and a second output coupler. The first waveguide has a first major surface and the second waveguide has a second major surface, which are disposed approximately parallel to each other. The first waveguide and the second waveguide are positioned as a combiner and allowing viewing an outside feed and information from an image source. The first input coupler diffracts light in the first field of view into the first waveguide and light in a second field of view reaches the second input coupler and is diffracted into the second waveguide.

Abstract: A display apparatus is provided. The display apparatus comprises a liquid crystal display device, a first polarizer and a diffractive optical element. The first polarizer is disposed on a light emitting side of the liquid crystal display device. An azimuth angle of a polarizing direction of the first polarizer is 90 degrees. The diffractive optical element is disposed on the light emitting side of the liquid crystal display device and comprises at least a first diffraction grating. An azimuth angle of a grating direction of the first diffraction grating is 10±30 degrees or 85±25 degrees.

Abstract: In a display apparatus, image light emitted from an image forming device is incident on an image light incidence portion of a light guide member after being diffracted by a second diffractive optical element, and emitted from an image light emission portion after moving forward in the light guide member. The image light emitted from the image light emission portion is diffracted by a first diffractive optical element and reaches the eyes of an observer. On a position where unnecessary external light is made incident on the light guide member, an external light noise reduction element which has a polarizing member and the like is provided. For this reason, even when the unnecessary external light is made incident on the light guide member, it is possible to inhibit the unnecessary external light from reaching the eye of the observer.

Abstract: A first article has a surface bearing a diffraction grating that comprises a plurality of elevated regions and recessed regions and a reflective coating that provides reflective diffraction within the article but is sufficiently thick to prevent diffraction outside the article. Alternatively, the reflective coating can be arranged to also provide reflective diffraction outside the article. A second article has a surface bearing a diffraction grating that comprises a plurality of elevated regions and recessed regions. Either (i) at least a portion of each ridge, or (ii) at least portion of each trench, comprises a material differing with respect to its refractive index or with respect to its optical transmissivity.

Abstract: A display system includes an optical component having a first and second surface, wherein the first surface comprises a diffractive optical element, and a projector system to create a projected image on the optical component. The projector includes an illumination source that emits electromagnetic radiation within a predetermined spectral band, an image generator that ascribes image characteristics to the radiation, and an optically-powered component that directs the radiation at the first surface of the optical component. The diffractive optical element reflects at least a portion of the radiation in a predetermined direction. The optical component has zero optical power for transmitted light. The optical component transmits at least a portion of the ambient scenery within a predetermined spectral band within a field-of-view of the projected image. The projected image maintains substantial boresight alignment with the ambient image.

Abstract: In an information recording medium, in which an information recording medium has diffraction grating cells arranged therein, a plurality of types of the diffraction grating cells make up one information recording area. At least one type of the diffraction grating cells included in the diffraction grating cells making up the information recording area are information recording elements, while the other types of the diffraction grating cells included in the diffraction grating cells making up the information recording area are information hiding elements. The information is recorded by two-dimensional arrangement of the diffraction grating cells constituting the information recording elements in the information recording area.

Abstract: A illumination device includes a light source, a diffractive optical element on which light emitted from the light source is made incident, and a superimposing optical system on which diffracted light emitted from the diffractive optical element is made incident. A direction of a principal ray in the center of the diffracted light coincides with an optical axis of the superimposing optical system. Consequently, it is possible to reduce an aberration due to the superimposing optical system and to emit illumination light having a more uniform illuminance distribution.

Abstract: The specification and drawings present a new apparatus and method for using exit pupil expanders (EPE) with spherical or aspheric non-flat substrates and a plurality of diffractive elements for expanding the exit pupil of a display for viewing in order to reduce image spreading. This can also enable improved image resolution and utilization of shorter focus distances.

Abstract: An optical waveguide is provided having at least first and second diffraction regions, the first diffraction region being arranged to diffract image-bearing light propagating along the waveguide so as to expand it in a first dimension and to turn the image-bearing light towards the second diffraction region, the second diffraction region being arranged to diffract the image-bearing light so as to expand it in a second dimension and to release it from the waveguide as a visible image. The first diffraction region is formed by first diffraction grating embedded within the waveguide, arranged to present a substantially similar profile to the image-bearing light when incident upon the grating from a given angle above or below the grating such that the polarisation of the image bearing light is rotated by substantially similar amounts, but in opposite directions, by successive interactions with the first diffraction region.

Abstract: The present invention provides a projection display (10) for projecting a colour image to a viewer (12) overlaid on a real world scene viewed through the display. The display comprises an image generator (16) for generating image bearing chromatic light for injection into a waveguide assembly (28) at a first range of field angles (44) and a second range of field angles (46). The waveguide assembly comprises a first waveguide (30) having a first input diffraction region (32) arranged to couple image bearing chromatic light in the first range of field angles into the first waveguide to propagate by total internal reflection; and a second waveguide (40) having a second input diffraction region (42) arranged to couple image bearing chromatic light in the second range of field angles into the second waveguide to propagate by total internal reflection.

Abstract: An image display device includes an image forming device, collimating optical system, and optical device, with the optical device including a light guide plate, first diffraction grating member and second diffraction grating member which are made up of a volume hologram diffraction grating, and with central light emitted from the pixel of the center of the image forming device and passed through the center of the collimating optical system being input to the light guide plate from the near side of the second diffraction grating member with a certain angle. Thus, the image display device capable of preventing occurrence of color irregularities, despite the simple configuration, can be provided.

Abstract: An optical apparatus includes an optical combiner, an image lens, and an external scene lens. The optical combiner has an eye-ward side and an external scene side and includes a partially reflective diffraction grating that is at least partially reflective to image light incident through the eye-ward side and at least partially transmissive to external scene light incident through the external scene side. A first mount is positioned to hold the image lens in an optical path of the image light to apply a first corrective prescription to the image light. A second mount is positioned to hold an external scene lens over the external scene side of the optical combiner to apply a second corrective prescription to the external scene light. The optical combiner combines the image light with the scene light to form a combined image that is corrected according to the first and second corrective prescriptions.

Abstract: Imaging device and method, the device including receiver optics, a diffractive and focusing surface, and a pair of diffractive and focusing arrangements, the receiver optics receiving radiation including a first wavelength selected from a first spectral band, and a second spectral band, where the first wavelength is substantially a multiplicative factor less than the midpoint of the second spectral band, the diffractive and focusing surface diffracting the first wavelength at an order of diffraction substantially equal to the multiplicative factor, and diffracting the second spectral band at a first order of diffraction, each of the diffractive and focusing arrangements diffracting, in turn, the first wavelength at a first order of diffraction, such that the first wavelength and the second spectral band emanating from the second diffractive and focusing arrangement focuses at a substantially common focal length and at a substantially common focal plane width.

Abstract: A transparent wearable data display having a source of collimated light a deflector for deflecting the collimated light into a scanned beam, and a first array including one column and integer N rows of switchable grating elements sandwiched between first and second parallel transparent substrates. The substrates together functioning as a first light guide, and a second array including M columns and N rows of switchable grating elements sandwiched between third and fourth parallel transparent substrates which together function as a second lightguide. Transparent electrodes are applied to opposing substrates. A first coupling for directing the scanned beam into a first TIR light path of the first lightguide along the first array column; and a second coupling for directing the first TIR light into a second TIR path of the second lightguide along a row of elements of the second array.

Abstract: The invention relates to a film (1) and a process for its production. The film (1) comprises a light-permeable replication lacquer layer (2) with a diffractive relief structure (3) formed in a first side (21) of the replication lacquer layer (2), a light-permeable colour lacquer layer (4), formed only in areas, arranged on the relief structure (3), and a reflective layer (5), formed at least in areas, arranged on the first side (21) of the replication lacquer layer (2). In areas (63) of the film (1) where the colour lacquer layer (4) and the reflective layer (5) overlap, the colour lacquer layer (4) is arranged between the replication lacquer layer (2) and the reflective layer (5).

Abstract: The present invention provides for a diffractive element comprising a diffractive optical microstructure consisting of a modulated structure of a diffractive type which upon illumination by diffused ambient light creates a two-dimensional image to be viewed by an observer upon tilting or rotating the device or by varying lighting direction, wherein the diffractive modulated structure of the device consists of various generally parameterised special optical elements with specifically prescribed groove shapes, wherein each groove shape, position, center(s), and line thickness, are described by functions describing those dependencies which are variables of the positional coordinate of the optical element.

Abstract: The various embodiments include a near-eye display having a transmissive display and a diffractive micro-lens array. The transmissive display may be positioned relative to the diffractive micro-lens array so that the distance between the transmissive display and the diffractive micro-lens array is be approximately equal to focal length of the diffractive micro-lens array. The transmissive display may also be positioned relative to the diffractive micro-lens array so that a percentage of light emitted from the transmissive display is diffracted by the micro-lens array and collimated into focus on a retina of a human eye. The transmissive display may be further positioned relative to the diffractive micro-lens array so that light from a real world scene passes through transparent portions of the transmissive display and is diffracted by the micro-lens array out of focus of the human eye.

Abstract: Methods create images viewable under different selected angles on optical storage devices and other photosensitive surfaces and optical storage devices with super-imposed images. Generally, a photosensitive surface is exposed with multiple diffraction patterns creating super-imposed images. These diffraction patterns create super-imposed images on the photosensitive surfaces, which can be read by either a human or a computer.

Abstract: An optical effect disc, has a transparent substrate and a surface optical structure, and an optical recording media combining the optical effect disc. The surface optical structure may be a computer-generated hologram optical structure or a micro-lens array structure for showing the effect of brightening or peep prevention, or a diffraction gating structure for achieving a three-dimensional visual effect. The optical effect disc or the optical recording media may include an image forming layer for forming an image to be shown by the optical effect disc with corresponding visual effect. The optical effect disc or the optical recording media may include an adhesive layer for attaching the optical effect disc to the optical recording media.

Abstract: A first optical arrangement is configured to couple into an apparatus a first component of a light beam having a wavelength within a first spectral range; a second optical arrangement configured to couple a second component of the light beam having a wavelength within a different second spectral range; a third optical arrangement configured to expand the first component in a first dimension to create an expanded first component; a fourth optical arrangement configured to expand, in a second dimension, the expanded first component to create a further expanded first component, and to output the further expanded first component; a fifth optical arrangement configured to expand the second component in the second dimension to create an expanded second component; and a sixth optical arrangement configured to expand, in the first dimension, the expanded second component to create a further expanded second component, and to output the further expanded second component.

Abstract: The specification and drawings present a new apparatus and method for using a three-dimensional (3D) diffractive element (e.g., a 3D diffractive grating) for expanding in one or two dimensions the exit pupil of an optical beam in electronic devices. Various embodiments of the present invention can be applied, but are not limited, to forming images in virtual reality displays, to illuminating of displays (e.g., backlight illumination in liquid crystal displays) or keyboards, etc.

Abstract: A virtual-image projector comprises a laser configured to form a narrow beam, first and second dilation optics, first and second redirection optics each having a diffraction grating, and a controller. The first dilation optic is arranged to receive the narrow beam and to project a one-dimensionally dilated beam into the second dilation optic. The second dilation optic is arranged to receive the one-dimensionally dilated beam and project a two-dimensionally dilated beam. The first and second redirection optics are each operatively coupled to a transducer. The first redirection optic is arranged to direct the narrow beam into the first dilation optic at a first entry angle. The second redirection optic is configured to direct the one-dimensionally dilated beam into the second dilation optic at a second entry angle. The controller is configured to bias the transducers to vary the first and second entry angles.

Abstract: The specification and drawings present a new apparatus and method for providing color separation in an exit pupil expander system that uses a plurality of diffractive elements for expanding the exit pupil of a display in an electronic device for viewing by introducing a selectively absorbing area or areas in the exit pupil expander.

Abstract: The present invention relates to an isotropic zero-order diffractive color filter, to a method to manufacture an embossing tool and to a method to manufacture such a filter. The zero-order diffractive color filter comprises diffractive microstructures and a wave-guiding layer, wherein the diffractive microstructures possess a short range ordering over at least four times the period of the microstructures, and the diffractive microstructures possess a long range disordering over length scales of more than 100 ?m.

Abstract: An image combiner for a viewing device, such as a night vision device, is disclosed for combining a first image, such as generated symbology, with a second image, such as a view of an outside scene in reduced lighting conditions. A waveguide is provided for capturing the first image from a first viewing direction, and for directing the first image in a second viewing direction, the second viewing direction being substantially coincident with a viewing direction of the second image, such that the first image can combine with the second image. At least a portion of the waveguide is arranged to substantially transmit the second image, such that the second image can pass substantially through the waveguide.

Abstract: An exterior part (200) includes (a) a structure color generation portion (210) having a minute shape (structure color generation region (211)) formed therein, light in a visible light range being produced from the minute shape by a physical phenomenon such as interference or diffraction with the incidence of light, and (b) a resin portion (220) that is made of resin having a light transmitting property and serves as the outer surface of a product, (c) the structure color generation portion (210) and the resin portion (220) are formed by molding, and (d) the structure color generation portion (210) is made of resin different from the resin of the resin portion (220), and covered with the resin portion (220).

Abstract: The specification and drawings present a new apparatus and method for providing a wide field-of-view as well as illumination uniformity in exit pupil expanders (EPE) using stacked EPE substrates (or plates) with non-symmetric exit pupil expansion that use a plurality of diffractive elements for expanding the exit pupil of a display for viewing.

Abstract: This document describes various apparatuses embodying, and techniques for implementing, a virtual image device. The virtual image device includes a projector and a lens configured to generate a virtual image as well as two diffraction gratings, substantially orthogonally-oriented to each other, that act to increase a field-of-view of the virtual image. The virtual image device can be implemented as a pair of eyeglasses and controlled to generate the virtual image in front of lenses of the eyeglasses so that a wearer of the eyeglasses, looking through the lenses of the eyeglasses, sees the virtual image.

Abstract: An optical device exhibiting a color shift upon rotation is disclosed. The optical device has a textured surface having a relief structure finer than a human eye resolution but large enough not to exhibit diffraction effects. The textured surface is coated with an interference thin film that exhibits a color shift with tilt. A uniform color seen at one angle of rotation changes to another uniform color when the optical device is rotated in its own plane. A method of manufacturing of such an optical device, as well as the use of the optical device as an optical security and authentication element, is also disclosed.

Abstract: A security device includes an optically variable device (OVD) having diffraction-based micro-optics including at least one moiré magnified visual representation of a micro-object. A diffractive structure provides micro-objects with unique optical effects when the OVD is viewed through the micro-object structure from a predetermined relative observation point. In addition to magnifying the micro-objects, the diffractive structure can impart optical effects such as change in observed color, enhanced contrast, animation of the observed visual representation, and change in size or shape of the observed visual representation. The micro-objects and the diffractive structure can be disposed on the same or different portions of a substrate. A method of making OVDs, and an article employing such OVDs are also disclosed.

Abstract: A virtual image display device with an optical waveguide to guide, by internal total reflection, parallel pencil groups meeting a condition of internal total reflection, a first reflection volume hologram grating to diffract and reflect the parallel pencil groups incident upon the optical waveguide from outside and traveling in different directions as they are so as to meet the condition of internal total reflection inside the optical waveguide and a second reflection volume hologram grating to project the parallel pencil groups guided by internal total reflection inside the optical waveguide as they are from the optical waveguide by diffraction and reflection thereof so as to depart from the condition of internal total reflection inside the optical waveguide.

Abstract: An optical device comprising an optical grating structure embedded between media of substantially the same optical refractive index, the structure having an optical coating at the interface between the two media, wherein the structure comprises grating facets inclined relative to the interface plane such that, in use, anomalous optical effects due to coating are substantially reduced.

Abstract: A near-to-eye optical system includes an optically transmissive substrate having a see-through display region and a repeating pattern of diffraction elements. The repeating pattern of diffraction elements is disposed across the see-through display region of the optically transmissive substrate and organized into a reflective diffraction grating that bends and focuses computer generated image (“CGI”) light impingent upon the reflective diffraction grating. The see-through display region is at least partially transmissive to external ambient light impingent upon an exterior side of the optically transmissive substrate and at least partially reflective to the CGI light impingent upon an interior side of the optically transmissive substrate opposite the exterior side.

Abstract: In an optical system, first green light reflected by a first diffractive optical element propagates in a left direction by repeating total reflection within a first light guide unit, is reflected by a third diffractive optical element, and is guided to a left eye. First red light reflected by a fifth diffractive optical element propagates in a left direction by repeating total reflection within a second light guide unit, is reflected by a seventh diffractive optical element, and is guided to a left eye. First blue light reflected by a ninth diffractive optical element is reflected by an eleventh diffractive optical element, and is guided to a left eye.

Abstract: An optical method of displaying an expanded colour image comprising extracting from input light bearing said coloured image a first spectral portion and a second spectral portion such that together the two portions contain sufficient information for the image to be displayed in substantially its original colours, separately expanding the two spectral portions each in two dimensions and recombining the expanded spectral portions to display the expanded colour image.

Abstract: A diffractive combiner for head-up color display device comprises a first optical diffraction grating configured to diffract, in a direction of diffraction, light of a first incident wavelength on the first grating in a direction of incidence, a second optical diffraction grating configured to diffract, in the same direction of diffraction, light of a second incident wavelength on the second grating in the direction of incidence. The first and second optical diffraction gratings are formed in relief on first and second opposed faces of the combiner. The first and/or the second grating is formed as a wavelength multiplexed optical diffraction grating and configured to diffract, in the direction of diffraction, light of a third incident wavelength on the first and/or second optical diffraction grating in the direction of incidence.

Abstract: The invention relates to a method for marking an object (1) during the production thereof, comprising the molding of at least one grating structure (10) on or in the surface of the object (1). To this end, said grating structure has a grating constant which permits observation by the naked eye of the diffraction structures which can be generated by visible light. The at least one grating structure (10) is generated by a molding process of the object (1), in which the mold used is equipped with a negative version of said grating structure. The object (1) at least partially consists of a soft polymer, in particular PVC-P, wherein the molding process is carried out as an injection molding process using an open mold.

Abstract: A flat substrate bears a set of flat, coplanar diffraction gratings; a jewelry mounting is secured to the substrate. The gratings are arranged to occupy corresponding areas of the substrate that are arranged to correspond to a two-dimensional projection of multiple, non-coplanar facets of a three-dimensional gemstone. Each grating differs from one or more other gratings with respect to grating wavevector direction so that each grating differs from at least one other grating with respect to direction of dispersion of spectrally dispersed output directions of a diffracted portion of light incident on the gratings along a given input direction. The grating wavevectors are spatially distributed among the corresponding gratings to form two or more subsets of three or more gratings along which subsets the corresponding grating wavevector direction of each grating of the subset varies monotonically with position of that grating along a given dimension of the substrate.

Abstract: A film (1) which includes at least one transparent replicating layer (2) having a diffractive relief structure (3) and a reflective layer, the reflective layer being formed by at least one pigmented lake layer (4), and the film (1, 1?, 1?) showing a latent optically variable effect produced by the diffractive relief structure (3), and the use thereof. Further a method for the production of such a film.

Abstract: A display apparatus and a liquid crystal display device are provided. The display apparatus comprises a display device for displaying an image and a diffractive optical element. The diffractive optical element comprises pixel unit regions. Each of the pixel unit regions has a long pixel side and a short pixel side adjacent to each other. The diffractive optical element is disposed on a light emitting side of the display device and comprises first grating regions and second grating regions. The first grating regions have a first diffraction grating. The second grating regions have a second diffraction grating. An azimuth angle of the first diffraction grating is different from an azimuth angle of the second diffraction grating.

Abstract: In the method for creating color patterns for technical applications and visible for the human eye by means of diffraction gratings through light irradiation, diffraction grating arrays are produced directly on a solid body surface in a laser microstructuring process by at least one laser installation in the nanosecond range or in the pico- or femtosecond range, each diffraction grating array being composed of subareas (81) whose longitudinal dimension has a value below the resolving ability of the eye and which contain at least one pixel (81, 82, 83), a pixel being a limited diffraction grating structure for producing a spectral color. The direct application of such color-producing diffraction grating structures to a solid body surface enables a large variety of decorative and authentication possibilities ranging from embossing tools to jewellery.

Abstract: A display including one or more first relief structures is provided. Each of the one or more first relief structures includes a smooth first reflection surface and a plurality of protrusions or recesses. Each top surface of the protrusions or each bottom of the recesses is a smooth second reflection surface parallel to the first reflection surface. Each of the one or more first relief structures is configured to display a mixed color as a structural color by mixing a plurality of wavelength components of visible light wavelengths. Also provided is a labeled article that includes the display, and an article supporting the display.

Abstract: A first article has a surface bearing a diffraction grating that comprises a plurality of elevated regions and recessed regions and a reflective coating that provides reflective diffraction within the article but is sufficiently thick to prevent diffraction outside the article. Alternatively, the reflective coating can be arranged to also provide reflective diffraction outside the article. A second article has a surface bearing a diffraction grating that comprises a plurality of elevated regions and recessed regions. Either (i) at least a portion of each ridge, or (ii) at least portion of each trench, comprises a material differing with respect to its refractive index or with respect to its optical transmissivity.

Abstract: A virtual image display device with an optical waveguide to guide, by internal total reflection, parallel pencil groups meeting a condition of internal total reflection, a first reflection volume hologram grating to diffract and reflect the parallel pencil groups incident upon the optical waveguide from outside and traveling in different directions as they are so as to meet the condition of internal total reflection inside the optical waveguide and a second reflection volume hologram grating to project the parallel pencil groups guided by internal total reflection inside the optical waveguide as they are from the optical waveguide by diffraction and reflection thereof so as to depart from the condition of internal total reflection inside the optical waveguide.