Patent Description:
Displays may be used to form still or moving images. Some displays may use a display panel to form images. Examples of such display panels include Light Emitting Diode (LED) display panels, Liquid Crystal Display (LCD) panels, and the like. In addition, some displays may use projectors to project still or moving images. Small displays may be used to form, or as a part of, mobile or wearable devices. For example, some displays may form or be part of a wearable heads-up display.

According to an implementation of the present specification there is provided an optical element including: a light guide; an incoupler optically coupled to the light guide; and a beam splitter disposed in an optical path of a display beam between the incoupler and a light engine to generate the display beam, the display beam including a first beam and a second beam, the beam splitter to split the display beam to form a first offspring beam including the first beam and a first portion of the second beam, and to form a second offspring beam including a second portion of the second beam, the first offspring beam and the second offspring beam incident upon the incoupler at a first incidence position and a second incidence position respectively, the first incidence position different than the second incidence position, the incoupler to direct at least a portion of each of the first offspring beam and the second offspring beam into the light guide to form an incoupled first offspring beam and an incoupled second offspring beam respectively.

The second beam may have a color associated with at least a wavelength that is longer than corresponding wavelengths associated with a corresponding color of the first beam.

The display beam may further include a third beam; and the beam splitter may be to split the display beam to form: the first offspring beam including the first beam, the first portion of the second beam, and the third beam; and the second offspring beam including the second portion of the second beam.

The optical element may further include a further beam splitter disposed in a corresponding optical path of the first offspring beam between the beam splitter and the incoupler, the further beam splitter to split the first offspring beam to form a third offspring beam including the first beam and a third portion of the second beam, and to form a fourth offspring beam including a fourth portion of the second beam.

The optical element may further include a further beam splitter disposed in a corresponding optical path of the second offspring beam between the beam splitter and the incoupler, the further beam splitter to split the second offspring beam to form a third offspring beam including a third portion of the second beam and a fourth offspring beam including a fourth portion of the second beam.

The beam splitter may include an about <NUM>/<NUM> beam splitter.

The incoupled second offspring beam may have a bounce length in the light guide; and a distance between the first incidence position and the second incidence position may be other than an integer multiple of the bounce length.

The optical element may further include an outcoupler optically coupled to the light guide, the outcoupler to direct at least a corresponding portion of each of the incoupled first offspring beam and the incoupled second offspring beam out of the light guide to form outcoupled beams propagating towards an eye of a user to form an image viewable by the user.

The beam splitter may include a dichroic partial reflector.

The incoupler may include a diffractive optical element.

According to another implementation of the present specification there is provided a method of operating a display to form an image viewable by a user, the method including: generating a display beam at a light engine, the display beam including a first beam and a second beam; splitting the display beam using a beam splitter to form a first offspring beam including the first beam and a first portion of the second beam, and to form a second offspring beam including a second portion of the second beam; directing the first offspring beam towards an incoupler to become incident upon the incoupler at a first incidence position, the incoupler optically coupled to a light guide; directing the second offspring beam towards the incoupler to become incident upon the incoupler at a second incidence position different than the first incidence position; directing, using the incoupler, at least a portion of each of the first offspring beam and the second offspring beam into the light guide to form an incoupled first offspring beam and an incoupled second offspring beam respectively; and directing, using an outcoupler, at least a corresponding portion of each of the incoupled first offspring beam and the incoupled second offspring beam out of the light guide to form outcoupled beams propagating towards an eye of the user to form the image viewable by the user.

The generating the display beam including the first beam and the second beam at the light engine may include generating the second beam having a color associated with at least a wavelength that is longer than corresponding wavelengths associated with a corresponding color of the first beam.

The generating the display beam may include generating the display beam including the first beam, the second beam, and a third beam; and the splitting the display beam may include splitting the display beam using the beam splitter to form: the first offspring beam including the first beam, the first portion of the second beam, and the third beam; and the second offspring beam including the second portion of the second beam.

The method may further include: splitting the first offspring beam using a further beam splitter to form: a third offspring beam including the first beam and a third portion of the second beam; and a fourth offspring beam including a fourth portion of the second beam.

The method may further include: splitting the second offspring beam using a further beam splitter to form: a third offspring beam including a third portion of the second beam; and a fourth offspring beam including a fourth portion of the second beam.

The splitting the display beam may include splitting the display beam using an about <NUM>/<NUM> beam splitter.

The directing the first offspring beam towards the incoupler and the directing the second offspring beam towards the incoupler may include directing the first offspring beam towards the incoupler to become incident upon the incoupler at the first incidence position and directing the second offspring beam towards the incoupler to become incident upon the incoupler at the second incidence position respectively, a distance between the first incidence position and the second incidence position being other than an integer multiple of a bounce length of the incoupled second offspring beam in the light guide.

The splitting the display beam may include splitting the display beam using the beam splitter including a dichroic partial reflector.

The directing at least the portion of each of the first offspring beam and the second offspring beam into the light guide may include directing, using the incoupler including a diffractive optical element, at least the portion of each of the first offspring beam and the second offspring beam into the light guide.

In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not necessarily drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn are not necessarily intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.

In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed implementations. However, one skilled in the relevant art will recognize that implementations may be practiced without one or more of these specific details, or with other methods, components, materials, and the like. In other instances, well-known structures associated with light sources have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the implementations.

Unless the context requires otherwise, throughout the specification and claims which follow, the word "comprise" and variations thereof, such as, "comprises" and "comprising" are to be construed in an open, inclusive sense, that is as "including, but not limited to.

As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its broadest sense, that is as meaning "and/or" unless the content clearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are for convenience only and do not interpret the scope or meaning of the implementations.

Throughout this specification and the appended claims, the term "carries" and variants such as "carried by" are generally used to refer to a physical coupling between two objects. The physical coupling may be direct physical coupling (i.e. with direct physical contact between the two objects) or indirect physical coupling that may be mediated by one or more additional objects. Thus, the term carries and variants such as "carried by" are meant to generally encompass all manner of direct and indirect physical coupling, including without limitation: carried on, carried within, physically coupled to, secured to, and/or supported by, with or without any number of intermediary physical objects therebetween.

Displays may use optical elements to guide and manipulate light to form images. Such optical elements may cause non-uniformities in the displayed images. Some of these non-uniformities may include variations in intensity or color balance across the field of the image. The field may include the array of pixels that form the image. Some of these non-uniformities may be detectable by a viewer of the display. The viewer of the display may also be described as the user of the display.

In some examples, an optical element may include a light guide and an incoupler (IC) optically coupled to the light guide. Moreover, in some examples, the IC may include a diffractive optical element, such as a surface relief grating (SRG), a hologram, or the like. The IC may receive a display beam generated by a light engine of the display that incorporates the optical element. The IC may then direct at least a portion of the display beam into the light guide to form an incoupled beam. The incoupled beam may then propagate within the light guide.

Furthermore, in some examples, the optical element may also include an outcoupler (OC). In addition, in some examples, the OC may also include a diffractive optical element such as a SRG, a hologram, or the like. The OC may be optically coupled to the light guide. Once the incoupled beam propagating within the light guide becomes incident upon the OC, the OC may direct at least a portion of the incoupled beam out of the light guide to form an outcoupled beam propagating towards an eye of a user of the display to form an image viewable by the user. It will be appreciated that the light guide can also be referred to as a waveguide. Example optical elements are described in greater detail in relation to <FIG>.

In color displays, the display beam may include beams of different colors. For example, the display beam may include red, green, and blue constituent beams. Different colors or combinations of colors may also be used. In some examples, the IC may direct each color beam of the display light into the light guide at a different angle based on the color (i.e., wavelength) of the beam. This, in turn, may cause the different color constituent beams of the display beam to have different bounce lengths within the light guide. As a result, beams with shorter bounce lengths may become incident upon the OC at bounce positions that are more closely spaced apart compared to the incidence positions of beams with relatively longer bounce lengths.

This difference between the spacings of the bounce positions of the different color beams on the OC may cause non-uniformities in the image displayed using the optical element. In some examples, such non-uniformities may include color balance non-uniformities. In some example optical elements, color beams corresponding to longer wavelengths may have a longer bounce length in the light guide (and correspondingly further spaced apart incidence positions on the OC) compared to color beams corresponding to relatively shorter wavelengths. This, in turn, may distort the color balance by favoring the colors of the color beams corresponding to the relatively shorter wavelengths, which may cause color balance non-uniformities in images formed using the display.

In order to reduce such image non-uniformities the light of one or more of the color beams at a given angle is introduced to the IC in multiple positions , thereby filling in, or reducing the size of, the spaces between the bounce positions of the beams of light. For example, two red beams, designated R1 and R2 respectively can be introduced to the IC at different positions. The bounce positions of the beam R2 in the light guide are closer to the bounce positions of the beam R1 than the distance between the bounce positions of the beam R1, thereby reducing non-uniformities in the red light. <FIG> show example optical elements in which a color beam is introduced to the OC in multiple positions.

<FIG>, in turn, shows a flowchart of an example method of operating a display, which method may also be used to introduce a color beam into the outcoupler in multiple positions to fill in or reduce the size of the spaces between the bounce positions of the beams. <FIG> show example displays and display components which may incorporate the optical elements described herein.

Turning now to <FIG>, a schematic representation of an example system <NUM> is shown. System <NUM> may be used to form or project an image viewable by an eye <NUM> of a viewer. System <NUM> may also be referred to or described as an image projection device, a display device, a display system, or a display. The viewer may also be described as a user of system <NUM>. System <NUM> may include a light engine <NUM> to generate a beam of output light <NUM>. In some examples, light engine <NUM> may include a light source <NUM> to generate output light <NUM>. Output light <NUM> may also be described as a display beam. In some examples, light engine <NUM> may generate a display beam including a plurality of different color beams. Such multi-color display beams may allow system <NUM> to form color images.

Moreover, in some examples, light source <NUM> may include at least one laser, at least one light emitting diode, and the like. Light engine <NUM> may also include a spatial modulator <NUM> to receive output light <NUM> from light source <NUM>. In some examples, spatial modulator <NUM> may include a movable reflector, a micro-electro-mechanical system (MEMS), a digital micromirror device (DMD), and the like. In some examples, spatial modulator <NUM> may be part of a relay optic of system <NUM>.

While <FIG> shows light engine <NUM> as including spatial modulator <NUM>, it is contemplated that in some examples light engine <NUM> need not include spatial modulator <NUM> or light source <NUM>. In some examples, light engine <NUM> may include a micro-display, or other light sources suitable for forming an image.

Furthermore, system <NUM> may include a display optic <NUM> to receive output light <NUM> from light engine <NUM> and direct the output light towards eye <NUM> of a user of the WHUD to form an image viewable by the user. In some examples, display optic <NUM> may include a light guide and an IC optically coupled to the light guide. Moreover, in some examples, display optic <NUM> may also include an OC optically coupled to the light guide. Furthermore, in some examples the display optic may be, or may include, one or more of the optical elements described herein, such as the optical elements described in relation to <FIG>, and the like.

Moreover, in some examples system <NUM> may be a part of or incorporated into a wearable heads-up display (WHUD). Such a heads-up display may have different designs or form factors, such as the form factor of eyeglasses, as is described in greater detail in relation to <FIG>. In examples where system <NUM> is in the form factor of glasses, display optic <NUM> may be on or in a lens of the glasses.

In addition, in some examples light engine <NUM> may include a controller <NUM> in communication with light source <NUM> and spatial modulator <NUM>. Controller <NUM> may control light source <NUM> and spatial modulator <NUM> to project an image. In some examples, the image to be projected may be a still image, a moving image or video, an interactive image, a graphical user interface, and the like.

In some examples, the controllers described herein such as controller <NUM> may include a processor in communication with a non-transitory processor-readable medium. The processor-readable medium may include instructions to cause the processors to control the light source and the spatial modulator to form images viewable by the user of system <NUM>. Moreover, in some examples the controllers may be free-standing components, while in other examples the controllers may include functional modules incorporated into other components of their respective systems.

Furthermore, in some examples the controllers or their functionality may be implemented in other ways, including: via Application Specific Integrated Circuits (ASICs), in standard integrated circuits, as one or more computer programs executed by one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs executed by one or more controllers (e.g., microcontrollers), as one or more programs executed by one or more processors (e.g., microprocessors, central processing units, graphical processing units), as firmware, and the like, or as a combination thereof.

Turning now to <FIG>, a partial-cutaway perspective view of an example wearable heads-up display (WHUD) <NUM> is shown. WHUD <NUM> includes a support structure <NUM> that in use is worn on the head of a user and has the general form factor and appearance of an eyeglasses (e.g. sunglasses) frame. Eyeglasses or sunglasses may also be generically referred to as "glasses". Support structure <NUM> may carry components of a system to display an image, such as system <NUM>. For example, light engine <NUM> may be received in a space <NUM> in a side arm of support structure <NUM>.

The spatial modulator of the systems described herein may be received in or be part of a component located in or near space <NUM> of support structure <NUM>. The spatial modulator in turn may direct the output light onto a display optic <NUM> carried by a lens <NUM> of support structure <NUM>. In some examples, display optic <NUM> may be similar in structure or function to display optic <NUM>. Moreover, in some examples display optic <NUM> may be, or may include, one or more of the optical elements described herein, such as the optical elements described in relation to <FIG>, and the like.

Turning now to <FIG>, a schematic cross-sectional representation is shown of an example lens <NUM> of an example WHUD. The components in <FIG> are not cross-hatched to allow for a clearer illustration of the path of an example ray of light traversing these components. In some examples, lens <NUM> may be used as lens <NUM> in WHUD <NUM>. Lens <NUM> has embedded within it a display optic, which display optic may be, or include an optical element. It is contemplated that in some examples, the optical element may include one or more of the optical elements described herein, such as the optical elements described in relation to <FIG>, and the like.

The optical element includes a light guide <NUM>, and an IC <NUM> and an OC <NUM> affixed to, embedded in, or integrated with light guide <NUM>. IC <NUM> may direct at least a portion of output light <NUM> into light guide <NUM> to form an incoupled beam. OC <NUM>, in turn, may outcouple from light guide <NUM> a portion of the incoupled beam to form an outcoupled beam propagating towards eye <NUM> of a viewer. While not shown in <FIG>, it is contemplated that in some examples, OC <NUM> may also act an exit pupil expander (EPE) and generate a plurality of exit pupils (EPs) that may enter eye <NUM> and become viewable by the user of the WHUD incorporating lens <NUM>.

Moreover, it is contemplated that in some examples, the display optic shown in <FIG> may be used as display optic <NUM> in system <NUM>. In some examples, light guide <NUM> may guide light within it using total internal reflection. IC <NUM> may receive an incoming beam of light, such as output light <NUM> generated by light source <NUM>. IC <NUM> may then redirect output light <NUM> towards light guide <NUM> at an angle that allows output light <NUM> to enter light guide <NUM>, and to travel through or within light guide <NUM>. Total internal reflection may prevent output light <NUM> from leaking from the walls of light guide <NUM>.

Once output light <NUM> that is travelling in light guide <NUM> reaches and becomes incident upon OC <NUM>, OC <NUM> may direct a portion of output light <NUM> out of light guide <NUM> and towards eye <NUM> of a user. In some examples, the combination of light guide <NUM>, IC <NUM>, and OC <NUM> may be described as an optical element. Such an optical element may be used as, or as a part of, display optic <NUM> in system <NUM> or display optic <NUM> in WHUD <NUM>.

<FIG>, in turn, shows a schematic cross-sectional representation of an example lens <NUM> of an example WHUD. The components in <FIG> are not cross-hatched to allow for a clearer illustration of the path of an example ray of light traversing these components. Lens <NUM> may have a similar structure and function as lens <NUM>. In addition, lens <NUM> may be used in similar displays or WHUDs as lens <NUM>. A difference between lenses <NUM> and <NUM> is that in the optical element of lens <NUM> an IC <NUM> is disposed proximate a surface <NUM> of light guide <NUM> opposite another surface <NUM> that carries OC <NUM>. In this configuration, output light <NUM> propagating from spatial modulator <NUM> passes through light guide <NUM> before becoming incident upon IC <NUM>.

In some examples, IC <NUM> may include a diffractive optical element. Moreover, in some examples, IC <NUM> may include a hologram disposed proximate surface <NUM> of light guide <NUM>. Furthermore, in some examples, IC <NUM> may include a SRG at or near surface <NUM>. It is also contemplated that in some examples, the OC may also include a diffractive optical element disposed at or near surface <NUM> of light guide <NUM>. In some examples, the combination of light guide <NUM>, IC <NUM>, and OC <NUM> may be described as an optical element. The optical element of lens <NUM> may also be used as, or as a part of, display optic <NUM> in system <NUM> or display optic <NUM> in WHUD <NUM>.

<FIG> shows a schematic cross-sectional representation of an example optical element <NUM>. Optical element <NUM> includes a light guide <NUM> and an IC <NUM> optically coupled to light guide <NUM>. In some examples, light guide <NUM> may include glass, an optical grade plastic, or other optical grade materials suitable for conducting light. Moreover, in some examples, IC <NUM> may include a diffractive optical element such as a SRG, a hologram, and the like. IC <NUM> may receive a display beam <NUM> generated by a light engine (not shown in <FIG>). IC <NUM> may then direct at least a portion of display beam <NUM> into light guide <NUM> to form an incoupled beam <NUM>. While not shown in <FIG>, it is contemplated that in some examples optical element <NUM> may also include an OC optically coupled to light guide <NUM>. In some examples, this OC may be carried by light guide <NUM>. Similarly, while the optical elements shown in <FIG> are shown without an OC, it is contemplated that in some examples, these optical elements may also each include a corresponding OC optically coupled to, or carried by, their respective light guides.

<FIG> also shows a distance <NUM> between bounce positions of incoupled beam <NUM>. As discussed above, in some examples the distance <NUM> may be a function of the color or wavelength of display beam <NUM>. In some examples, a shorter wavelength display beam may have a shorter distance between bounce positions and a relatively longer wavelength display beam may have a relatively longer distance between bounce positions.

<FIG> also shows a schematic cross-sectional representation of optical element <NUM>. In <FIG>, a display beam <NUM> is received by IC <NUM>. Display beam <NUM> includes three constituent color beams. In this description, "constituent color beams" may also be referred to as "color constituent beams". The color beam having the shortest wavelength is incoupled by IC <NUM> into light guide <NUM> to form incoupled beam <NUM>. The color beam having the longest wavelength is incoupled by IC <NUM> into light guide <NUM> to form incoupled beam <NUM>. Moreover, the color beam having the wavelength intermediate between the shortest and the longest wavelengths is incoupled by IC <NUM> into light guide <NUM> to form incoupled beam <NUM>.

As shown in <FIG>, incoupled beam <NUM> having the shortest wavelength has a shortest distance <NUM> between bounce positions in light guide <NUM>. Incoupled beam <NUM> having the longest wavelength has a longest distance <NUM> between bounce positions in light guide <NUM>. Furthermore, incoupled beam <NUM> having the intermediate wavelength has a distance <NUM> between bounce positions in light guide <NUM>. Distance <NUM> is intermediate between distances <NUM> and <NUM>.

Turning now to <FIG>, a schematic, cross-sectional representation of an example optical element <NUM> is shown. Optical element <NUM> includes light guide <NUM> and IC <NUM> optically coupled to light guide <NUM>. In addition, optical element <NUM> includes a beam splitter <NUM> disposed in the optical path of display beam <NUM> from a light engine (not shown in <FIG>) that generated the display beam to IC <NUM>. Beam splitter <NUM> splits display beam <NUM> to form a first offspring beam <NUM> and a second offspring beam <NUM>.

In some examples, beam splitter <NUM> may split display beam <NUM> by transmitting a first portion of display beam <NUM> to form offspring beam <NUM> and by reflecting a second portion of display beam <NUM> to form offspring beam <NUM>. As display beam <NUM> includes one color beam, offspring beams <NUM> and <NUM> have the same color or wavelength. Optical element <NUM> also includes a reflector <NUM> to direct offspring beam <NUM> towards IC <NUM>. Offspring beam <NUM> then becomes incident upon IC <NUM> at an incidence position <NUM>. Beam splitter <NUM> directs offspring beam <NUM> towards IC <NUM>, where offspring beam <NUM> then becomes incident upon IC <NUM> at an incidence position <NUM>.

As shown in <FIG>, incidence positions <NUM> and <NUM> may be spaced from one another. IC <NUM> then directs a portion of each of offspring beams <NUM> and <NUM> into light guide <NUM> to form a first incoupled offspring beam <NUM> and a second incoupled offspring beam <NUM> respectively. As incoupled offspring beams <NUM> and <NUM> have the same wavelengths, they have distance <NUM> between bounces in light guide <NUM>. Since the incidence positions <NUM> and <NUM> are offset from one another on IC <NUM>, the bounce positions of incoupled offspring beams <NUM> and <NUM> on walls of light guide <NUM> are also correspondingly offset from one another.

As discussed above, incoupled offspring beams <NUM> and <NUM> have a wavelength that is the same or substantially the same as the wavelength of display beam <NUM>. The offsetting of bounce positions of the incoupled offspring beams in light guide <NUM> may allow for the incoupled beams having the wavelength of display beam <NUM> to have a distance <NUM> between bounces of the different beams that is shortened relative to distance <NUM>. That is, the distance <NUM> represents the distance between a bounce position of the beam <NUM> and the closest bounce position of the beam <NUM>, and this distance <NUM> is less than the distance <NUM>.

So long as the distance between incidence positions <NUM> and <NUM> is other than an integer multiple of spacing <NUM>, the offset between incidence positions <NUM> and <NUM> translates into a corresponding offset between the bounce positions of the incoupled offspring beams in light guide <NUM>. This offset between the bounce positions in the light guide, in turn, yields a distance, between bounce positions that is shortened compared to distance <NUM>, thereby reducing non-uniformities.

While optical element <NUM> uses a reflector <NUM> to direct offspring beam <NUM> towards IC <NUM>, it is contemplated that in some examples, different types, numbers, or arrangements of optical components may be used to direct the offspring beams onto the IC such that they become incident upon the IC at respective incidence positions that are offset from one another. For example, it is contemplated that in some examples, optical element <NUM> need not include reflector <NUM>. In such examples, beam splitter <NUM>, alone or in combination with one or more other optical components, may be used to direct the offspring beams towards IC <NUM>. Examples of such optical components may include reflectors, lenses, prisms, light guides, and the like.

Turning now to <FIG>, a schematic, cross-sectional representation is shown of an example optical element <NUM>. Similar to optical element <NUM>, optical element <NUM> may include light guide <NUM> and IC <NUM> optically coupled to light guide <NUM>. Optical element <NUM> may also include a beam splitter <NUM> to receive a display beam <NUM> generated by a light engine (not shown in <FIG>). Display beam <NUM> includes a first beam <NUM> and a second beam <NUM>. In some examples, beams <NUM> and <NUM> may include different colors or wavelengths.

In <FIG> constituent beams <NUM> and <NUM> of display beam <NUM> are shown as two distinct beams for illustrative purposes, and it is contemplated that in some examples, beams <NUM> and <NUM> may be coincident as constituent beams of a single display beam <NUM>. It is also contemplated that in some examples, display beam <NUM> may include more than two constituent color beams each having a different color.

Beam splitter <NUM> is disposed in the optical path of display beam <NUM> from the light engine to IC <NUM>. While <FIG> shows beam splitter <NUM> disposed at a given position and orientation relative to light guide <NUM>, IC <NUM>, and display beam <NUM>, it is contemplated that in some examples, the beam splitter may be positioned or oriented differently relative to light guide <NUM>, IC <NUM>, and display beam <NUM>.

Beam splitter <NUM> may split display beam <NUM> by transmitting beam <NUM>, while partially reflecting beam <NUM> to form beam <NUM> and partially transmitting beam <NUM> to form beam <NUM>. In this manner, beam splitter <NUM> may split display beam <NUM> to form a first offspring beam <NUM> and a second offspring beam <NUM>. First offspring beam <NUM> may include beam <NUM> and beam <NUM>. While in <FIG> constituent beams <NUM> and <NUM> of offspring beam <NUM> are shown as two distinct beams for illustrative purposes, it is contemplated that in some examples, beams <NUM> and <NUM> may be coincident as constituent beams of a single offspring beam <NUM>.

In some examples, beam splitter <NUM> may include a dichroic partial reflector, and the like. Moreover, in some examples, beam splitter <NUM> may include an about <NUM>/<NUM> beam splitter. Such a <NUM>/<NUM> beam splitter may split beam <NUM> such that the intensity of beams <NUM> and <NUM> is about the same. It is also contemplated that in some examples, beam splitter <NUM> may be other than a <NUM>/<NUM> beam splitter. In still other embodiments, beam splitter <NUM> can be a polarization beam splitter.

Optical element <NUM> may include a reflector <NUM> to direct offspring beam <NUM> towards IC <NUM> to become incident upon IC <NUM> at an incidence position <NUM>. Beam splitter <NUM> may direct offspring beam <NUM> to become incident upon IC <NUM> at incidence position <NUM>. Incidence position <NUM> may be offset from incidence position <NUM> on IC <NUM> by a distance <NUM>. IC <NUM> may, in turn, direct at least a portion of beams <NUM>, <NUM>, and <NUM> into light guide <NUM> to form incoupled beams <NUM>, <NUM>, and <NUM> respectively. As beams <NUM>, <NUM>, and <NUM> are offspring beams of display beam <NUM>, incoupled beams <NUM>, <NUM>, and <NUM> may also be referred to as incoupled offspring beams.

Beam <NUM> may have a color associated with a wavelength that is longer than the wavelength associated with the color of beam <NUM>. In some examples, beam <NUM> may be red, and beam <NUM> may be green or blue. In some examples, other colors and color combinations may also be used. As shown in <FIG>, offspring beams <NUM> and <NUM> (and their corresponding incoupled beams <NUM> and <NUM>) of beam <NUM> have a larger distance <NUM> between bounce positions in light guide <NUM> compared to the relatively shorter distance <NUM> between bounce positions of offspring beam <NUM> (and its corresponding incoupled beam <NUM>).

Distance <NUM> between incidence positions <NUM> and <NUM> causes the bounce positions of incoupled beams <NUM> and <NUM> on the wall of light guide <NUM> to be offset from one another. This offsetting effect takes place so long as distance <NUM> is other than an integer multiple of bounce length <NUM>. The offset between the bounce positions of incoupled beams <NUM> and <NUM> on the wall of light guide <NUM> may cause the distance <NUM> between corresponding bounce positions of the incoupled offspring beams of beam <NUM> (that is, the distance between the corresponding bounces of the offspring beams) to be shortened relative to distance <NUM>.

This shortening distance between bounce positions may reduce the difference between the distance <NUM> associated with beam <NUM> having a shorter wavelength and the distance <NUM> associated with beam <NUM> having a relatively longer wavelength. In other words, the difference between the distance <NUM> and the distance <NUM> is reduced compared to the relatively larger difference between the distance <NUM> and the distance <NUM>. This, in turn, may allow for reducing the difference between the distance between bounce positions of a longer-wavelength color constituent (e.g. red) of display beam <NUM> and the distance between bounce positions of a relatively shorter-wavelength color constituent (e.g. green or blue) of display beam <NUM>.

Reducing the wavelength- or color-dependent differences between the distance between bounce positions of the various color constituents of the display beam in the light guide may, in turn, reduce color balance non-uniformities that may be caused by such bounce length differences in images formed by displays that use optical elements such as optical element <NUM>.

While not shown in <FIG>, it is contemplated that in some examples, optical element <NUM> may also include an OC optically coupled to light guide <NUM>. This OC may receive incoupled offspring beams <NUM>, <NUM>, and <NUM> via light guide <NUM>. The OC may then direct at least a corresponding portion of each of the incoupled offspring beams out of light guide <NUM> to form outcoupled beams (not shown in <FIG>) propagating towards an eye of a user to form an image viewable by the user.

Turning now to <FIG>, a schematic cross-sectional representation of an example optical element <NUM> is shown. Optical element <NUM> may be similar to optical element <NUM>. Optical element <NUM> may include a beam splitter <NUM> positioned to receive a display beam <NUM> including three color constituent beams. Beam splitter <NUM> may split display beam <NUM> to form a first offspring beam <NUM> including the first and third color constituent beams <NUM>, <NUM> and a first portion of the second color constituent beam <NUM> of display beam <NUM>. Moreover, beam splitter <NUM> may split display beam <NUM> to form a second offspring beam <NUM> including a second portion of the second color constituent beam of display beam <NUM>.

In order words, beam splitter <NUM> may transmit the first and third color constituent portions of display beam <NUM>. Moreover, beam splitter <NUM> may partially transmit the second color constituent portion of display beam <NUM> to form offspring beam <NUM>, and may partially reflect the second color constituent portion of display beam <NUM> to form offspring beam <NUM>. In some examples, the second color constituent beam may be associated with a color associated with one or more wavelengths that are longer that the wavelengths associated with the colors of the first and third color constituent beams of display beam <NUM>. In other words, in some examples, the color constituent beam being split by beam splitter <NUM> into a partially reflected portion and a partially transmitted portion may be the color constituent beam whose color is associated with the longest wavelength of the wavelengths associated with the colors of the constituent beams of display beam <NUM>.

Furthermore, in some examples, the second color constituent beam may be associated with red, and the first and third color constituent beams may be associated with green and blue. Other colors and color combinations are also contemplated. Optical element <NUM> may also include a reflector <NUM> to direct offspring beam <NUM> towards IC <NUM>. It is also contemplated that in some examples, optical element <NUM> need not include reflector <NUM>, in which examples beam splitter <NUM>, alone or in combination with one or more additional optical components, may direct offspring beam <NUM> towards IC <NUM>. IC <NUM> may then direct at least a portion of each of beams <NUM>, <NUM>, <NUM>, and <NUM> to form incoupled beams <NUM>, <NUM>, <NUM>, and <NUM> respectively.

Turning now to <FIG>, a schematic, cross-sectional representation is shown of an example optical element <NUM>. Optical element <NUM> may be similar to optical element <NUM>. A difference between optical elements <NUM> and <NUM> may be that optical element <NUM> includes a further beam splitter <NUM> disposed in the optical path of first offspring beam <NUM> between beam splitter <NUM> and IC <NUM>. Beam splitter <NUM> may split offspring beam <NUM> to form a further offspring beam <NUM> including beam <NUM> and an offspring beam <NUM>. Offspring beam <NUM> may include a portion of beam <NUM> transmitted by beam splitter <NUM>.

Beam splitter <NUM> may split offspring beam <NUM> to also form a yet further offspring beam <NUM>. Beam <NUM> may include a portion of beam <NUM> reflected by beam splitter <NUM>. In this manner, offspring beams <NUM> and <NUM> may include respective portions of beam <NUM>, while offspring beam <NUM> includes beam <NUM> and beam <NUM>, wherein beam <NUM> is a further portion of beam <NUM>. In some examples, beam <NUM> may have a color associated with one or more wavelengths that are longer than the wavelengths associated with the color of beam <NUM>.

IC <NUM> may direct at least a portion of beams <NUM>, <NUM>, <NUM>, and <NUM> to form incoupled offspring beams <NUM>, <NUM>, <NUM>, and <NUM> respectively. Using the additional beam splitter <NUM> to form the additional offspring beam <NUM> incident upon IC <NUM> further reduces the distance between the incidence positions on IC <NUM> of the offspring beams of beam <NUM>, which in turn further reduces the distance between bounce positions of incoupled offspring beams of beam <NUM> in light guide <NUM>.

It is contemplated that in some examples, optical element <NUM> may be used with a display beam that has three or more color constituent beams, similar to display beam <NUM> shown in <FIG>. Moreover, while <FIG> shows a particular position and orientation of beam splitters <NUM> and <NUM>, it is contemplated that in some examples, different arrangements and orientations of beam splitters <NUM> and <NUM> may be used. In addition, it is contemplated that in some examples optical element <NUM> need not include reflector <NUM>. Moreover, in some examples, optical element <NUM> may include an OC optically coupled to light guide <NUM>, which OC may outcouple corresponding portions of incoupled offspring beams <NUM>, <NUM>, <NUM>, and <NUM> to form an image viewable by a user of a display incorporating optical element <NUM>.

Turning now to <FIG>, a schematic, cross-sectional representation is shown of an example optical element <NUM>. Optical element <NUM> may be similar to optical element <NUM>. A difference between optical elements <NUM> and <NUM> may be that optical element <NUM> includes a further beam splitter <NUM> disposed in the optical path of second offspring beam <NUM> between beam splitter <NUM> and IC <NUM>. Beam splitter <NUM> may split offspring beam <NUM> to form further offspring beams <NUM> and <NUM>. Offspring beam <NUM> may include a portion of beam <NUM> transmitted by beam splitter <NUM>, and offspring beam <NUM> may include another portion of beam <NUM> reflected by beam splitter <NUM>. Furthermore, in some examples, optical element <NUM> may also include a further reflector <NUM> to direct offspring beam <NUM> towards IC <NUM>.

In this manner, offspring beams <NUM> and <NUM> may include respective portions of beam <NUM>, while offspring beam <NUM> includes beam <NUM> and beam <NUM>, wherein beam <NUM> is also a portion of beam <NUM>. In some examples, beam <NUM> my have a color associated with one or more wavelengths that are longer than the wavelengths associated with the color of beam <NUM>.

It is contemplated that in some examples, optical element <NUM> may be used with a display beam that has three or more color constituent beams, similar to display beam <NUM> shown in <FIG>. Moreover, while <FIG> shows a particular position and orientation of beam splitters <NUM> and <NUM> and reflectors <NUM> and <NUM>, it is contemplated that in some examples, different arrangements and orientations of beam splitters <NUM> and <NUM> or reflectors <NUM> and <NUM> may be used. In addition, it is contemplated that in some examples optical element <NUM> need not include reflectors <NUM> or <NUM>. Moreover, in some examples, optical element <NUM> may include an OC optically coupled to light guide <NUM>, which OC may outcouple corresponding portions of incoupled offspring beams <NUM>, <NUM>, <NUM>, and <NUM> to form an image viewable by a user of a display incorporating optical element <NUM>.

While the optical elements shown in <FIG> have their respective ICs positioned on a surface of the light guide similar to the configuration shown in <FIG>, it is contemplated that In some examples, the optical elements shown in <FIG> may have their ICs positioned on an opposing surface of the light guide, similar to the configuration shown in <FIG>. It is also contemplated that in some examples, the optical elements may have their ICs positioned relative to their light guide in a configuration other than those shown in <FIG> or <FIG>.

Moreover, the optical elements shown in <FIG> and the other optical elements described herein may be used as display optics, or as a part of the display optics, in lenses <NUM> and <NUM>, in WHUD <NUM>, and in system <NUM>.

Turning now to <FIG>, a flowchart is shown of an example method <NUM> of operating a display to form an image viewable by a user. Method <NUM> may be used to reduce color balance non-uniformities of the images formed by the display. In some examples, method <NUM> may be used to operate system <NUM>, WHUD <NUM>, and the other systems and displays described herein. Moreover, in some examples, method <NUM> may be performed using, among other components, the optical elements described herein in relation to <FIG>, which optical elements may in turn be used as a component in system <NUM>, WHUD <NUM>, and the other systems and displays described herein.

At box <NUM> of method <NUM>, a display beam may be generated at a light engine of the display. In some examples, the display beam may include a first beam and a second beam. Furthermore, at box <NUM> the display beam may be split using a beam splitter to form a first offspring beam including the first beam and a first portion of the second beam, and to form a second offspring beam including a second portion of the second beam.

Moreover, at box <NUM> the first offspring beam may be directed towards an incoupler to become incident upon the incoupler at a first incidence position. The incoupler may be optically coupled to a light guide. At box <NUM>, in turn, the second offspring beam may be directed towards the incoupler to become incident upon the incoupler at a second incidence position different than the first incidence position.

Furthermore, at box <NUM> at least a portion of each of the first offspring beam and the second offspring beam may be directed into the light guide using the incoupler, to form an incoupled first offspring beam and an incoupled second offspring beam respectively. In addition, at box <NUM> at least a corresponding portion of each of the incoupled first offspring beam and the incoupled second offspring beam may be directed out of the light guide using an outcoupler to form outcoupled beams propagating towards an eye of the user to form the image viewable by the user.

In some examples, generating the display beam including the first beam and the second beam at the light engine may include generating the second beam having a color associated with at least a wavelength that is longer than corresponding wavelengths associated with a corresponding color of the first beam.

Moreover, in some examples, generating the display beam may include generating the display beam including the first beam, the second beam, and a third beam. Splitting the display beam may include splitting the display beam using the beam splitter to form the first offspring beam including the first beam, the first portion of the second beam, and the third beam, and the second offspring beam including the second portion of the second beam.

Furthermore, in some examples, method <NUM> may further include splitting the first offspring beam using a further beam splitter to form a third offspring beam including the first beam and a third portion of the second beam, and a fourth offspring beam including a fourth portion of the second beam. In addition, in some examples, method <NUM> may further include splitting the second offspring beam using a further beam splitter to form a third offspring beam including a third portion of the second beam, and a fourth offspring beam including a fourth portion of the second beam.

In some examples, splitting the display beam may include splitting the display beam using an about <NUM>/<NUM> beam splitter. Moreover, in some examples, the beam splitter may include a dichroic partial reflector, and the like. Furthermore, in some examples, directing at least the portion of each of the first offspring beam and the second offspring beam into the light guide may include directing, using the incoupler including a diffractive optical element, at least the portion of each of the first offspring beam and the second offspring beam into the light guide.

In addition, in some examples, directing the first offspring beam towards the incoupler and directing the second offspring beam towards the incoupler may include directing the first offspring beam towards the incoupler to become incident upon the incoupler at the first incidence position and directing the second offspring beam towards the incoupler to become incident upon the incoupler at the second incidence position respectively. The distance between the first incidence position and the second incidence position may be other than an integer multiple of a bounce length of the incoupled second offspring beam in the light guide.

It is contemplated that method <NUM> and the other methods described herein may be performed by system <NUM>, WHUD <NUM>, and the other systems, displays, and devices described herein. It is also contemplated that method <NUM> and the other methods described herein may be performed by systems or devices other than the systems and devices described herein. In addition, it is contemplated that system <NUM>, WHUD <NUM>, optical elements <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and the other systems, devices, and optical elements described herein may have some or all of the features and perform some or all of the functions described herein in relation to method <NUM> and the other methods described herein. Moreover, system <NUM>, WHUD <NUM>, optical elements <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and the other systems, devices, and optical elements described herein may have features and perform functions other than those described herein in relation to method <NUM> and the other methods described herein.

Moreover, while <FIG> and <FIG> show a given optical element having a given arrangement of light guide, incoupler, and outcoupler, it is contemplated that in some examples the optical element may have a different structure, and that the light guide, incoupler, and outcoupler may be arranged differently relative to one another. In addition, while some of the examples provided herein are described in the context of laser projectors and WHUDs, it is contemplated that the functions and methods described herein may be implemented in or by display systems or devices which may not use laser projectors or be WHUDs.

Throughout this specification and the appended claims, infinitive verb forms are often used. Examples include, without limitation: "to form," "to direct," "to split," "to generate," and the like. Unless the specific context requires otherwise, such infinitive verb forms are used in an open, inclusive sense, that is as "to, at least, form," to, at least, direct," "to, at least, split," and so on.

The above description of illustrated example implementations, including what is described in the Abstract, is not intended to be exhaustive or to limit the implementations to the precise forms disclosed. Although specific implementations of and examples are described herein for illustrative purposes, various equivalent modifications can be made without departing from the scope of the disclosure, as will be recognized by those skilled in the relevant art. Moreover, the various example implementations described herein may be combined to provide further implementations.

Claim 1:
An optical element comprising:
a light guide (<NUM>) having a first surface and a second surface opposite the first surface;
an incoupler (<NUM>) optically coupled to the light guide; and
a beam splitter (<NUM>, <NUM>, <NUM>) disposed in an optical path of a display beam between the incoupler and a light engine to generate the display beam, the display beam comprising a first beam and a second beam, the beam splitter to split the display beam to form a first offspring beam (<NUM>) comprising the first beam and a first portion of the second beam, and to form a second offspring beam (<NUM>) comprising a second portion of the second beam, the first offspring beam and the second offspring beam incident upon the incoupler at a first incidence position and a second incidence position respectively, the first incidence position different than the second incidence position, wherein
the incoupler is configured to direct at least a portion of the first and second offspring beam into the light guide to form a first and a second incoupled offspring beam, and wherein both the first and the second incoupled offspring beam bounce on the first and the second surface.