Method and system for eyebox expansion in display systems

A method includes receiving a light beam propagating along an optical path, converting, using a first diffractive element, a first portion of the light beam into a first circularly polarized beam, and a second portion of the light beam into a second circularly polarized beam. The method also includes converting, using a second diffractive element, the first circularly polarized beam into a first circularly polarized output beam, and the second circularly polarized beam into a second circularly polarized output beam.

BACKGROUND

Image displays, including near-eye displays, have been utilized in virtual reality and augmented reality systems. Typically, the resolution and field of view of the image, as well as the eyebox size, are system parameters of interest. Despite the progress in the area of optical systems, there is a need in the art for improved methods and systems related to image display systems.

DETAILED DESCRIPTION

Embodiments of the present disclosure are directed to, among other things, optical systems that can be utilized in conjunction with virtual reality and augmented reality systems. As described more fully herein, the optical systems provided by various embodiments of the present disclosure enable production of multiple output light beams from a single input light beam as well as optical switches that can shift or translate an image formed at an exit pupil of the optical system, thereby providing for an expanded eyebox and improved user experience.

FIG.1illustrates a schematic diagram of a laser beam scanning augmented reality system in accordance with an embodiment of the present disclosure. As illustrated inFIG.1, laser beam scanning augmented reality system100includes projector110, which in the embodiment illustrated inFIG.1utilizes red-green-blue (RGB) light engine112and micro-electro-mechanical (MEMS) scanning mirror114to scan the light beam produced by RGB light engine112across transreflective optical element120. In this exemplary embodiment, RGB light engine112produces light in the three primary colors, red, green, and blue sequentially and MEMS scanning mirror114scans this light across transreflective optical element120. InFIG.1, MEMS scanning mirror114is illustrated in a first scanning orientation and in an optional rotated scanning orientation. Beam shifting system116is included as element of projector110and the operation of beam shifting system116in producing eyebox expansion will be described more fully below.

As illustrated inFIG.1, the beginning of the row of the pixels forming the image is illustrated by scan line125and the end of the row of the pixels forming the image is illustrated by scan line127. In this embodiment, a raster scanning protocol is utilized to form the image, with the scanning of the light from projector110in the orthogonal direction (i.e., into and out of the plane of the figure) not shown for purposes of clarity. Although raster scanning is illustrated in this embodiment, the use of raster scanning is not required and other techniques and systems for forming an image can be utilized. Moreover, although laser scanning is illustrated inFIG.1, other projection techniques and systems can be utilized, including liquid crystal on silicon (LCOS) projectors, liquid crystal display (LCD) projectors, micro-light emitting diode (LED) projectors, and the like.

In the augmented reality system illustrated inFIG.1, transreflective optical element120is transmissive to light incident on transreflective optical element120from a side121opposite to the user and reflective to light incident from projector110on the side122facing the user, thereby directing the light from projector110to user's eye130as well as enabling the user to view the scene viewable through transreflective optical element120. In some implementations, transreflective optical element120includes diffractive elements, for example, holographic films, that are used to implement the reflective character of transreflective optical element120in relation to light from projector110. In other embodiments, reflective structures or combinations of diffractive and reflective structures are utilized to form an image at the exit pupil of laser beam scanning augmented reality system100. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. In the embodiment illustrated inFIG.1, exit pupil140of laser beam scanning augmented reality system100is formed at the pupil of user's eye130.

In virtual reality applications, transreflective optical element120can be replaced with a reflective optical element that does not allow light from the scene that would otherwise be viewable through transreflective optical element120to be transmitted to the user.

As illustrated inFIG.1, exit pupil140of laser beam scanning augmented reality system100is formed at the pupil of user's eye130. As will be evident to one of skill in the art, the eyebox refers to a volume at which the eye of the user receives an acceptable view of the image, usually defined with respect to a set of criteria. When the user moves their eye to view a different portion of the field of view, the motion of the eye can cause the user's pupil to move outside the eyebox. Accordingly, in augmented reality and virtual reality systems, it is advantageous to increase the size of the eyebox and, thereby, improve the user experience since the larger eyebox enables the user to shift the position of the pupil of the user's eye and still view the image produced by the projector.

Accordingly, various embodiments of the present disclosure generate multiple, spatially separated light beams that can be present at the exit pupil of laser beam scanning augmented reality system100, thereby increasing eyebox size and improving the user experience. Thus, as the user moves their eye to view different portions of the field of view, the light beam produced using projector110can be shifted in the plane of the exit pupil in order to provide an image aligned with the user's pupil and increase the size of the eyebox. As described more fully herein, in some embodiments, multiple images are formed sequentially in the plane of the exit pupil of laser beam scanning augmented reality system100in a manner such that the individual images are positioned to correspond to the position of the user's pupil as a function of time.

FIG.2Aillustrates a schematic diagram of a laser beam scanning augmented reality system in a first operating condition in accordance with an embodiment of the present disclosure. Referring toFIG.2A, light from projector110originates at location210, is reflected from transreflective optical element120, and forms an image at location212, which, in this case, aligns with the pupil of user's eye230, which is looking toward the left side of transreflective optical element120. Although inFIG.2A, location210and location212are illustrated as a point, it will be appreciated that the light produced by projector110can have a lateral extent at location210and the image formed at location212can have a lateral extent and be characterized by a resolution, for example, 1920×1080 pixels, or the like.

FIG.2Billustrates an image formed at an exit pupil of the laser beam scanning augmented reality system in the first operating condition in accordance with an embodiment of the present disclosure. Referring toFIG.2B, image220is centered on location212and forms a portion of larger field of view222. When the pupil of user's eye230is positioned at location212, the user is able to view the image produced using projector110.

FIG.2Cillustrates a schematic diagram of a laser beam scanning augmented reality system in a second operating condition in accordance with an embodiment of the present disclosure. In this second operating condition, light from projector110has been shifted to originate at location215rather than location210. Referring toFIGS.2A and2C, light from the projector is shifted in the x-y plane by a distance measured along the y-axis. Thus, a lateral shift is illustrated, with the propagation of the light beam being aligned with the longitudinal direction (i.e., the direction aligned with the z-axis) and the translation of the light beam occurring in the lateral plane (i.e., the x-y plane). Accordingly, light from projector110is reflected from transreflective optical element120and forms an image at location217. Although inFIG.2C, location215and location217are illustrated as a point, it will be appreciated that the light produced by projector110can have a lateral extent at location215and the image formed at location217can have a lateral extent and be characterized by a resolution, for example, 1920×1080 pixels, or the like.

In the embodiment illustrated inFIG.2C, the angle subtended by scan line250and scan line252is equal to the angle subtended by scan line254and scan line256. In other words, scan line250is parallel to scan line254and scan line252is parallel to scan line256. Thus, despite the shift in position of the light from projector110from location210to location215, the angular information present in the image is maintained in this embodiment. In other embodiments, the angular extent of the scanned light does not need to be constant (i.e., scan line250does not need to be parallel to scan line254and scan line252does not need to be parallel to scan line256) and, in addition to the lateral shift in the position of the light from projector110, the angle at which the light exits the projector can be modulated or varied, resulting in a modulation in the angle of the light from projector110, resulting in a corresponding shift in the position of the image formed at the exit pupil of the laser beam scanning augmented reality system.

FIG.2Dillustrates a shifted image formed at an exit pupil of the laser beam scanning augmented reality system in the second operating condition in accordance with an embodiment of the present disclosure. In this second operating condition, image225is centered on location217and forms a portion of larger field of view222. InFIG.2C, the pupil of the user's eye has been shifted by a lateral shift A with respect to the position illustrated inFIG.2A. Accordingly, the lateral shift in the position of the image from location212to location217enables the user to view the image, which is now aligned with the pupil of the user's eye since the user is now looking toward the right side of transreflective optical element120. As will be evident to one of skill in the art, a suitable eye tracking system can be utilized to track the position of the pupil of the user's eye and provide inputs to enable the corresponding shift in position of the image formed at the exit pupil of the laser beam scanning augmented reality system.

Thus, by shifting the position of the image at the exit pupil of the laser beam scanning augmented reality system in a manner that corresponds to the shift in the user's eye position/orientation, the user is able to view the image produced using projector110while looking in different directions.

FIG.3illustrates a schematic diagram of a beam multiplication system300in accordance with an embodiment of the present disclosure. Referring toFIG.3, light beam310is propagating along optical path312, which in this example, is aligned with the z-axis, also referred to as the longitudinal direction. Light beam310has a cross-sectional width of Win this embodiment and can be produced, for example, using a MEMS scanning mirror. The width W may characterize the beam waist of light beam310, for example, a beam waist of a Gaussian beam. Light beam310can be linearly polarized, for example, polarized to align with the x-axis or the y-axis, or can be unpolarized. Thus, for example, if the laser source is linearly polarized, the projector could maintain this linear polarization and produce a polarized beam as light beam310.

Light beam310is incident on a first diffractive element320, which converts a first portion of light beam310into a first circularly polarized beam propagating along a first predetermined direction and a second portion of light beam310into a second circularly polarized beam propagating along a second predetermined direction. As illustrated inFIG.3, light beam310is converted by first diffractive element320into a left-hand circularly polarized beam322propagating at an angle α and a right-hand circularly polarized beam324propagating at angle −α. For collimated light beam310, left-hand circularly polarized beam322and right-hand circularly polarized beam324are also collimated.

An exemplary first diffractive element320is a liquid-crystal-based Pancharatnam-Berry phase optical element (PBOE), which can be referred to as a holographic deflector, a cycloidal diffractive wave plate, or a PB deflector. Pancharatnam-Berry deflectors are planar holographic structures that can be implemented in the form of one or more diffractive films and utilize patterning of the orientation of the anisotropy axis to diffract incident light as well as convert unpolarized light or linearly polarized light into circularly polarized light. Thus, as illustrated inFIG.3, light beam310is diffracted by first diffractive element320to form first positive diffracted order (i.e., m=+1) left-hand circularly polarized beam322and to form first negative diffracted order (m=−1) right-hand circularly polarized beam324. In some embodiments, only the first positive diffracted order and the first negative diffracted order are produced by the interaction of light beam310and first diffractive element320, with the zero diffracted order, as well as higher positive and negative diffracted orders, being suppressed. As will be evident to one of skill in the art, the angles at which the diffracted orders exist as well as power distribution between the various diffracted orders are functions of the design of the Pancharatnam-Berry deflectors.

If light beam310is unpolarized and all diffracted orders other than the first positive diffracted order and the first negative diffracted order are suppressed, then 50% of the diffracted light will be present in left-hand circularly polarized beam322and 50% of the diffracted light will be present in right-hand circularly polarized beam324. Similarly, if light beam310is linearly polarized and all diffracted orders other than the first positive diffracted order and the first negative diffracted order are suppressed, then 50% of the diffracted light will be present in left-hand circularly polarized beam322and 50% of the diffracted light will be present in right-hand circularly polarized beam324.

A second diffractive element330is positioned a distance d, which can also be referred to as a longitudinal separation distance, from first diffractive element320and is aligned to be parallel to first diffractive element320. In some embodiments, the distance d is selected such that:

d>Wtan⁡(α),
where
sin(α)=λ/Λ,
where λ is the wavelength of the input light beam and A is the grating spacing of the diffractive elements.

Second diffractive element330receives left-hand circularly polarized beam322and right-hand circularly polarized beam324, which are propagating at angles α and −α, respectively. Second diffractive element330, which can be identical to first diffractive element320, thereby providing for the interchangeability of second diffractive element330and first diffractive element320, converts left-hand circularly polarized beam322into a right-hand circularly polarized output beam332propagating parallel to the optical path and right-hand circularly polarized beam324into a left-hand circularly polarized output beam334that is also propagating parallel to the optical path. Thus, the use of an unpolarized or linearly polarized input beam and first diffractive element320in combination with second diffractive element330results in conversion of the unpolarized or linearly polarized input beam into two circularly polarized beams as well as the multiplication of the single input beam into two output beams. The propagation direction of light beam310as well as right-hand circularly polarized output beam332and left-hand circularly polarized output beam334is along the direction of the optical path, i.e., aligned with the longitudinal z-axis. In other embodiments, first diffractive element320and second diffractive element330are not identical, for example, characterized by differing diffractive structure periodicity. If the second diffractive element330has a different diffractive structure periodicity than first diffractive element320, then second diffractive element330will be characterized by a diffraction angle different than diffraction angle α. As a result, right-hand circularly polarized output beam332and left-hand circularly polarized output beam334will propagate at an angle with respect to the direction of the optical path. Thus, although some embodiments discussed herein produce output beams propagating along the same direction as the input beam, this is not required and some embodiments may produce output beams propagating at an angle that is not aligned with the optical path.

Thus, as illustrated inFIG.3, the use of second diffractive element330results in a change in the handedness of the left-hand circularly polarized beam322as well as a redirection of the right-hand circularly polarized output beam332to propagate parallel to the optical path and a change in the handedness of the right-hand circularly polarized beam324as well as a redirection of the left-hand circularly polarized output beam334to propagate parallel to the optical path. The diffraction angle α and the distance d (i.e., the longitudinal separation distance) between first diffractive element320and second diffractive element330result in the lateral spatial separation of right-hand circularly polarized output beam334and left-hand circularly polarized output beam334by a separation distance s measured orthogonal to the optical path. Accordingly, various embodiments of the present disclosure provide systems that, depending on the distance d and the diffraction angle α, multiply a single input light beam (e.g., light beam310) into spatially separated output light beams that are laterally separated from each other by separation distance s (e.g., between right-hand circularly polarized output beam332and left-hand circularly polarized output beam334) measured orthogonal to the optical path. An optional absorber335may be positioned adjacent second diffractive element330to absorb light diffracted into the m=0 order by first diffractive element320. Accordingly, right-hand circularly polarized output beam332and left-hand circularly polarized output beam334do not overlap in some embodiments, but are laterally separated from each other. In other embodiments, right-hand circularly polarized output beam332and left-hand circularly polarized output beam334overlap to some extent, with lateral separation distance s being less than width W or equal to zero. As an example, if Gaussian beams are utilized and lateral separation distance s is equal to width 2 W, the tails of the Gaussian beams can overlap although the centers of the Gaussian beams are separated by lateral separation distance s. Referring toFIGS.2B and2D, the lateral shift A between image220and image225can be produced by utilizing the various embodiments of the present disclosure as described herein.

Therefore, the beam multiplication system illustrated inFIG.3enables the conversion of a single input beam into two output beams having a predetermined, lateral spatial separation distance s between the output beams. As described more fully below, althoughFIG.3illustrates a system with two output beams, multiple pairs of diffractive elements can be cascaded to generate additional output beams, for example, four output beams as illustrated inFIGS.4Aand5discussed more fully below. Moreover, by using active polarization control, the spatial separation functionality can be utilized to select an output beam positioned at a predetermined location with respect to the input beam, enabling shifting of the image formed at the exit pupil of a laser beam scanning augmented reality system, for example, to correspond to the location of the pupil of the user's eye. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG.4Aillustrates a schematic diagram of another beam multiplication system in accordance with an embodiment of the present disclosure. As will be described, beam multiplication system400produces four output beams, with a lateral, spatial separation between each of two sets of the output beams in both the y-direction as well as the x-direction.

Referring toFIG.4A, light beam410is propagating along optical path412, which in this example, is aligned with the z-axis, also referred to as the longitudinal direction. Light beam410has a cross-sectional width of Win this embodiment and can be produced, for example, using a MEMS scanning mirror. Light beam410can be linearly polarized, for example, polarized to align with the x-axis or the y-axis, or can be unpolarized. Thus, for example, if the laser source is linearly polarized, the projector could maintain this linear polarization and produce a polarized beam as light beam410.

Light beam410is incident on a first diffractive element420, which converts a first portion of light beam410into a first circularly polarized beam propagating along a first predetermined direction and a second portion of light beam410into a second circularly polarized beam propagating along a second predetermined direction. As illustrated inFIG.4A, light beam410is converted by first diffractive element420into a left-hand circularly polarized beam422(also referred to as a first circularly polarized beam) propagating at an angle α and a right-hand circularly polarized beam424(also referred to as a second circularly polarized beam) propagating at angle −α. For collimated light beam410, left-hand circularly polarized beam422and right-hand circularly polarized beam424are also collimated.

Thus, as illustrated inFIG.4A, light beam410is diffracted by first diffractive element420to form first positive diffracted order (i.e., m=+1) left-hand circularly polarized beam422and to form first negative diffracted order (m=−1) right-hand circularly polarized beam424. In some embodiments, only the first positive diffracted order and the first negative diffracted order are produced by the interaction of light beam410and first diffractive element420, with the zero diffracted order, as well as higher positive and negative diffracted orders being suppressed. As will be evident to one of skill in the art, the angles at which the diffracted orders exist as well as power distribution between the various diffracted orders are functions of the design of the Pancharatnam-Berry deflectors.

If light beam410is unpolarized and all diffracted orders other than the first positive diffracted order and the first negative diffracted order are suppressed, then 50% of the diffracted light will be present in left-hand circularly polarized beam422and 50% of the diffracted light will be present in right-hand circularly polarized beam424. Similarly, if light beam410is linearly polarized and all diffracted orders other than the first positive diffracted order and the first negative diffracted order are suppressed, then 50% of the diffracted light will be present in left-hand circularly polarized beam422and 50% of the diffracted light will be present in right-hand circularly polarized beam424. In some embodiments, the width W is conserved as light beams propagate through the various optical elements described herein, enabling beam multiplication and switching without changes in the beam size.

A second diffractive element430is positioned a distance d2, which can also be referred to as a longitudinal separation distance, from first diffractive element420and is aligned to be parallel to first diffractive element420. In comparison with the longitudinal separation distance d illustrated inFIG.3, the spacing between first diffractive element420and second diffractive element430enables left-hand circularly polarized beam422and right-hand circularly polarized beam424to be laterally separated from each other by a suitable distance such that the lateral spatial separation between all four light beams generated using beam multiplication system400results in non-overlapping light beams.

Second diffractive element430receives left-hand circularly polarized beam422and right-hand circularly polarized beam424, which are propagating at angles α and −α, respectively. Second diffractive element430, which can be identical to first diffractive element420, thereby providing for the interchangeability of second diffractive element430and first diffractive element420, converts left-hand circularly polarized beam422into a right-hand circularly polarized output beam432(also referred to as a first circularly polarized output beam) propagating parallel to the optical path and right-hand circularly polarized beam424into a left-hand circularly polarized output beam434(also referred to as a second circularly polarized output beam) that is also propagating parallel to the optical path. Thus, the use of an unpolarized or linearly polarized input beam and first diffractive element420in combination with second diffractive element430results in conversion of the unpolarized or linearly polarized input beam into two circularly polarized beams as well as the multiplication of the single input beam into two output beams. The propagation direction of light beam410as well as right-hand circularly polarized output beam432and left-hand circularly polarized output beam434is along the direction of the optical path, i.e., aligned with the longitudinal z-axis.

Thus, as illustrated inFIG.4A, the use of second diffractive element430results in a change in the handedness of the left-hand circularly polarized beam422as well as a redirection of the right-hand circularly polarized output beam434to propagate parallel to the optical path and a change in the handedness of the right-hand circularly polarized beam424as well as a redirection of the left-hand circularly polarized output beam434to propagate parallel to the optical path. The diffraction angle α and the distance d2(i.e., the longitudinal separation distance) between first diffractive element420and second diffractive element430result in the lateral spatial separation of right-hand circularly polarized output beam432and left-hand circularly polarized output beam434by a separation distance s2(e.g., between right-hand circularly polarized output beam432and left-hand circularly polarized output beam434). Accordingly, first diffractive element420and second diffractive element430, depending on the distance d2and the diffraction angle α, multiply a single input light beam (e.g., light beam410) into spatially separated output light beams that are laterally separated from each other by separation distance s2. The spatial separation of right-hand circularly polarized output beam432and left-hand circularly polarized output beam434occurs in the y-direction. As described below, a second stage of diffractive elements will utilize beams based on right-hand circularly polarized output beam432and left-hand circularly polarized output beam434as input beams in order to generate four output beams, each separated from the other output beams in both the y-direction and the x-direction.

FIG.4Billustrates a set of light beams present at a first location in the beam multiplication system illustrated inFIG.4A. At first location401in the lateral plane, light beam410has been converted into two output beams (i.e., right-hand circularly polarized output beam432and left-hand circularly polarized output beam434) spatially separated from each other in the lateral y-direction by a separation distance s2.

Referring once again toFIG.4A, quarter wave plate435is positioned along the optical path after first diffractive element420and second diffractive element430. Right-hand circularly polarized output beam432is converted by quarter wave plate435into linearly polarized input beam437(also referred to as a first linearly polarized beam) and left-hand circularly polarized output beam434is converted by quarter wave plate435into linearly polarized input beam439(also referred to as a second linearly polarized beam). As described more fully below, a second set of diffractive elements is utilized in order to multiply each of the two input beams to form two sets of output beams and to spatially separate each set of output beams by a distance measured along the x-direction, thereby providing four output beams located at different lateral positions in the x-y plane.

First, considering linearly polarized input beam437, this beam is incident on a third diffractive element440, which converts a first portion of linearly polarized input beam437into a first circularly polarized beam propagating along the first predetermined direction and a second portion of linearly polarized input beam437into a second circularly polarized beam propagating along the second predetermined direction. As illustrated inFIG.4A, left-hand circularly polarized beam442(also referred to as a third circularly polarized beam) is propagating at an angle α and right-hand circularly polarized beam444(also referred to as a fourth circularly polarized beam) is propagating at angle −α. Since linearly polarized input beam437was collimated, left-hand circularly polarized beam442and right-hand circularly polarized beam444are also collimated.

AlthoughFIG.4Aillustrates the diffraction of linearly polarized input beam437into a first positive diffracted order (i.e., m=+1) and a first negative diffracted order (m=−1) lying in the plane of the figure, it will be appreciated that left-hand circularly polarized beam442and right-hand circularly polarized beam444are propagating at angles ±α with respect to the plane of the figure. Thus, the orientation of third diffractive element440is aligned in order to diffract the input light into two diffracted orders with angles measured with respect to the x-axis.

A fourth diffractive element450is positioned a distance d2, which can also be referred to as a longitudinal separation distance, from third diffractive element440and is aligned to be parallel to third diffractive element440. Fourth diffractive element450receives left-hand circularly polarized beam442and right-hand circularly polarized beam444, which are propagating at angles α and −α lying in the x-z plane, respectively. Fourth diffractive element450, which can be identical to third diffractive element440, thereby providing for the interchangeability of fourth diffractive element450and third diffractive element440, converts left-hand circularly polarized beam442into a first right-hand circularly polarized output beam452(also referred to as a third circularly polarized output beam) propagating parallel to the optical path and right-hand circularly polarized beam444into a first left-hand circularly polarized output beam454(also referred to as a fourth circularly polarized output beam) that is also propagating parallel to the optical path.

Thus, in a manner similar to the first set of diffractive elements, third diffractive element440and fourth diffractive element450receive an input beam and provide two output beams, but with the two output beams spatially separated from each other by a separation distance measured along the x-axis. The propagation direction of first right-hand circularly polarized output beam452as well as first left-hand circularly polarized output beam454is along the direction of the optical path, i.e., aligned with the longitudinal z-axis.

Thus, as illustrated inFIG.4A, the use of fourth diffractive element450results in a change in the handedness of the left-hand circularly polarized beam442as well as a redirection of the first right-hand circularly polarized output beam452to propagate parallel to the optical path and a change in the handedness of the right-hand circularly polarized beam444as well as a redirection of the first left-hand circularly polarized output beam454to propagate parallel to the optical path.

Considering linearly polarized input beam439, this beam is incident on third diffractive element440, which converts a first portion of linearly polarized input beam439into a first circularly polarized beam propagating along the first predetermined direction and a second portion of linearly polarized input beam439into a second circularly polarized beam propagating along the second predetermined direction. As illustrated inFIG.4A, left-hand circularly polarized beam446(also referred to as a fourth circularly polarized beam) is propagating at an angle α and right-hand circularly polarized beam448(also referred to as a fifth circularly polarized beam) is propagating at angle −α. Since linearly polarized input beam439was collimated, left-hand circularly polarized beam446and right-hand circularly polarized beam448are also collimated.

AlthoughFIG.4Aillustrates the diffraction of linearly polarized input beam439into a first positive diffracted order (i.e., m=+1) and a first negative diffracted order (m=−1) lying in the plane of the figure, it will be appreciated that left-hand circularly polarized beam446and right-hand circularly polarized beam448are propagating at angles ±α with respect to the plane of the figure. Thus, the orientation of third diffractive element440is aligned in order to diffract the input light into two diffracted orders with angles measured with respect to the x-axis.

Fourth diffractive element450receives left-hand circularly polarized beam446and right-hand circularly polarized beam448, which are propagating at angles α and −α lying in the x-z plane, respectively. Fourth diffractive element450converts left-hand circularly polarized beam446into second right-hand circularly polarized output beam456(also referred to as a fifth circularly polarized output beam) propagating parallel to the optical path and right-hand circularly polarized beam448into second left-hand circularly polarized output beam458(also referred to as a sixth circularly polarized output beam) that is also propagating parallel to the optical path.

Thus, as illustrated inFIG.4A, the use of fourth diffractive element450results in a change in the handedness of left-hand circularly polarized beam446as well as a redirection of the second right-hand circularly polarized output beam456to propagate parallel to the optical path and a change in the handedness of right-hand circularly polarized beam448as well as a redirection of second left-hand circularly polarized output beam458to propagate parallel to the optical path.

In combination, the first set of diffractive elements and the second set of diffractive elements introduce, depending on diffraction angle α and the distance d2(i.e., the longitudinal separation distance) between the sets of diffractive elements, a lateral spatial separation s2of the four output beams in both the y-direction and the x-direction.

In other embodiments, if the diffraction angle associated with the diffractive elements and/or the longitudinal distance between adjacent diffraction elements in a set of diffractive elements is changed, the separation distances measured along the y-axis or the x-axis can be different. Thus, the lateral separation distance between beams can differ along different directions. Moreover, the output beams can propagate at an angle with respect to the direction of the optical path if the diffraction angles associated with the diffractive elements are different. Thus, embodiments provide both output beams aligned with the optical path and output beams propagating at angles that are not aligned with the optical path. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG.4Cillustrates a second set of light beams present at an output of the beam multiplication system illustrated inFIG.4A. At the output of beam multiplication system400, which can be referred to as a second location403in the lateral plane, linearly polarized input beam410has been converted into four output beams spatially separated from each other in the lateral y-direction by a separation distance s2and in the lateral x-direction by the separation distance s2. As illustrated inFIG.4C, image460and image462, which were produced based on linearly polarized input beam437, are centered on locations470and472, respectively. Image464and image466, which were produced based on linearly polarized input beam439, are centered on locations474and476, respectively. Accordingly, starting with a single linearly polarized input light beam410, four, laterally separated output light beams are produced using beam multiplication system400, increasing the eyebox for a user when the four, laterally separated output light beams are present at the pupil of a user's eye.

Thus, by using two sets of diffractive elements, each introducing a lateral separation between output beams along two axes, a linearly polarized input light beam has been converted into four output beams, each separated from adjacent output beams by a separation distance s2. By using active polarization control as described in relation toFIGS.8A-Cand9A-C, the beam multiplication and spatial separation functionality can be utilized to select an output beam positioned at a predetermined location with respect to the input beam, enabling shifting of the image formed at the exit pupil of a laser beam scanning augmented reality system, for example, to correspond to the location of the pupil of the user's eye. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG.5illustrates a schematic diagram of a beam multiplication system in accordance with another embodiment of the present disclosure. As will be described, beam multiplication system500produces four output beams, with a lateral, spatial separation between each of two sets of the output beams in both the y-direction as well as the x-direction.

Referring toFIG.5A, light beam510is propagating along optical path512, which in this example, is aligned with the z-axis (i.e., the longitudinal direction). Light beam510has a cross-sectional width of Win this embodiment and can be produced, for example, using a MEMS scanning mirror. Light beam510can be linearly polarized, for example, polarized to align with the x-axis or the y-axis, or can be unpolarized. Thus, for example, if the laser source is linearly polarized, the projector could maintain this linear polarization and produce a polarized beam as light beam510.

Light beam510is incident on a first diffractive element520, which converts light beam510into a left-hand circularly polarized beam propagating at an angle α with respect to the y-axis and a right-hand circularly polarized beam propagating at angle −α with respect to the y-axis. Since light beam510is collimated, the left-hand circularly polarized beam and right-hand circularly polarized beam that are produced after diffraction produced by first diffractive element520are also collimated. The operation of first diffractive element520is thus similar to that described with respect to first diffractive element420illustrated inFIG.4A.

The left-hand circularly polarized beam and the right-hand circularly polarized beam produced by first diffractive element520, propagating at an angle ±α with respect to the y-axis, respectively, are now diffracted by third diffractive element540. The operation of third diffractive element540is similar to that described with respect to third diffractive element440illustrated inFIG.4A. Namely, each of the left-hand circularly polarized beam and the right-hand circularly polarized beam is converted into two sets of left-hand circularly polarized and right-hand circularly polarized beams, propagating at angles ±α with respect to the x-axis. Referring toFIG.5, although only two beams are illustrated at location501between the sets of diffractive elements, it will be appreciated that four beams are present, a set of beams542propagating at angle α with respect to the y-axis and angles ±α with respect to the x-axis and a set of beams544propagating at angle −α with respect to the y-axis and angles ±α with respect to the x-axis.

In some embodiments, first diffractive element520and third diffractive element540are fabricated as films that are in close proximity. As an example, first diffractive element520could be fabricated as a holographic film on a first substrate, third diffractive element540could be fabricated as a holographic film on a second substrate, and the first substrate and second substrate could be joined together to form a single optical element.

In order to redirect the set of beams542and the set of beams544to propagate parallel to the optical path (i.e., along the z-direction), second diffractive element530and fourth diffractive element550are positioned a distance d from first diffractive element520and third diffractive element540. Diffraction by second diffractive element530and fourth diffractive element550also results in a change in the handedness of each of the four beams incident on second diffractive element530and fourth diffractive element550. Although only two beams are illustrated at location503after the second set of diffractive elements, it will be appreciated that four beams are present.

Accordingly, four output beams are generated after diffraction from second diffractive element530and fourth diffractive element550. The first set of output beams552and the second set of output beams554are laterally separated by lateral separation distance s measured along the y-axis. Each of the two beams making up the set of output beams552is laterally separated by lateral separation distance s measured along the x-axis and each of the two beams making up the set of output beams554is also laterally separated by lateral separation distance s measured along the x-axis. Thus, the two output beams included in the set of output beams552and the two output beams in the set of output beams554are each separated from adjacent output beams by a lateral spatial separation s in both the y-direction and the x-direction.

Thus, by using two sets of diffractive elements, the first set introducing angled light beams and the second set redirecting the beams to a direction parallel to the optical path and changing the handedness of the diffracted beams, a linearly polarized input beam has been converted into four output beams, each separated from adjacent output beams by a separation distance s. By using active polarization control as described in relation toFIGS.8A-Cand9A-C, the beam multiplication and spatial separation functionality can be utilized to select an output beam positioned at a predetermined location with respect to the input beam, enabling shifting of the image formed at the exit pupil of a laser beam scanning augmented reality system, for example, to correspond to the location of the pupil of the user's eye. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Therefore, beam multiplication system500illustrated inFIG.5provides four output beams in a manner similar to that achieved using beam multiplication system400illustrated inFIG.4. Beam multiplication system400utilizes distance d2to separate first diffractive element420and second diffractive element430, as well as an additional distance d2to separate third diffractive element440and fourth diffractive element450, resulting in beam multiplication system400having a longitudinal thickness on the order of ˜2d2. In contrast, in beam multiplication system500, only third diffractive element540and second diffractive element530are separated by distance d, enabling beam multiplication system500to have a longitudinal thickness on the order of ˜d.

FIG.6illustrates an example of a flow for operating a beam multiplication system in accordance with an embodiment of the present disclosure. The method600of operating the beam multiplication system includes receiving a light beam propagating along an optical path (610). As discussed in relation to the operation of beam multiplication system300illustrated inFIG.3, the light beam can be an unpolarized beam or a linearly polarized beam. The optical path is parallel to the longitudinal z-axis in some embodiments and the multiple output beams provided by the beam multiplication system are laterally separated from each other in the lateral plane (i.e., the x-y plane) orthogonal to the optical path.

The method also includes converting, using a first diffractive element, a first portion of the light beam into a first circularly polarized beam propagating along a first predetermined direction (612) and converting, using the first diffractive element, a second portion of the light beam into a second circularly polarized beam propagating along a second predetermined direction (614). The first predetermined direction can be a direction associated with a first positive diffracted order (m=+1) lying in the y-z plane and the second predetermined direction can be a direction associated with a first negative diffracted order (m=−1) that also lies in the y-z plane. Thus, both the first predetermined direction and the second predetermined direction can be parallel to a plane (e.g., the y-z plane).

The method further includes converting, using a second diffractive element, the first circularly polarized beam into a first circularly polarized output beam (616) and converting, using the second diffractive element, the second circularly polarized beam into a second circularly polarized output beam (618). The first circularly polarized output beam can propagate in a direction parallel to the optical path and the second circularly polarized output beam can propagate in the direction parallel to the optical path. In other embodiments, the output beams can propagate along directions aligned at a non-zero angle with respect to the optical path. Thus, embodiments of the present disclosure provide for the multiplication of a single input beam into two or more output beams having a predetermined, lateral separation between the output beams, with the method illustrated inFIG.6providing two output beams separated from each other by a separation distance measured along an axis (e.g., the y-axis) orthogonal to the optical path (e.g., the z-axis).

In some embodiments, the first diffractive element and the second diffractive element, which can be liquid-crystal-based Pancharatnam-Berry phase optical elements, are interchangeable. The light beam can be characterized by a linearly polarized state or an unpolarized state. Moreover, the first circularly polarized beam can be characterized by a right-hand circular polarization and the second circularly polarized beam can be characterized by a second handedness opposite the first handedness (i.e., a left-hand circular polarization). In this case, the first circularly polarized output beam is characterized by the second handedness (i.e., a right-hand circular polarization) and the second circularly polarized output beam is characterized by the first handedness (i.e., a left-hand circular polarization).

In an alternative embodiment, the method includes converting, using a quarter wave plate, the first circularly polarized output beam into a first linearly polarized light beam and the second circularly polarized output beam into a second linearly polarized light beam. The method also includes converting, using a third diffractive element, the first linearly polarized light beam into a first circularly polarized beam propagating in a third predetermined direction and a second circularly polarized beam propagating in a fourth predetermined direction as well as the second linearly polarized light beam into a third circularly polarized beam propagating in the third predetermined direction and a fourth circularly polarized beam propagating in the fourth predetermined direction. The method further includes changing, using a fourth diffractive element the first circularly polarized beam into a first circularly polarized output beam propagating parallel to the optical path, the second circularly polarized beam into a second circularly polarized output beam propagating parallel to the optical path, the third circularly polarized beam into a third circularly polarized output beam propagating parallel to the optical path, and the fourth circularly polarized beam into a fourth circularly polarized output beam propagating parallel to the optical path.

The third predetermined direction and the fourth predetermined direction can be parallel to a second plane (e.g., the x-z plane) orthogonal to the plane (e.g., the y-z plane) discussed above. Thus, using embodiments of the present disclosure, each of the first circularly polarized output beam, the second circularly polarized output beam, the third circularly polarized output beam, and the fourth circularly polarized output beam can be separated from each other by a lateral separation distance measured in a plane (e.g., the x-y plane) orthogonal to the optical path (e.g., the z-axis).

It should be appreciated that the specific steps illustrated inFIG.6provide a particular method of operating a beam multiplication system according to an embodiment of the present disclosure. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments of the present disclosure may perform the steps outlined above in a different order. Moreover, the individual steps illustrated inFIG.6may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG.7Aillustrates a schematic diagram of an optical switch in a first operating condition in accordance with an embodiment of the present disclosure. Light beam710is input into optical switch700by passing through polarization rotator705. In this embodiment, polarization rotator705produces a right-hand circularly polarized beam to serve as light beam710. Light beam710has a width W. Since light beam710is a right-hand circularly polarized beam, if all diffracted orders other than the first positive diffracted order and the first negative diffracted order are suppressed, the handedness of the input light beam is changed to a left-hand circularly polarized beam and the output light beam is diffracted into the first positive diffracted order as a result of diffraction from first diffractive element720. Thus, first diffractive element720diffracts light beam710into the first positive diffracted order and converts light beam710into left-hand circularly polarized beam722, which is propagating at an angle α. As discussed in relation toFIG.3, second diffractive element730is positioned a distance d, i.e., a longitudinal separation distance, from first diffractive element720and is aligned to be parallel to first diffractive element720. Second diffractive element730receives left-hand circularly polarized beam722propagating at angles α. Second diffractive element730, which can be identical to first diffractive element720, thereby providing for the interchangeability of second diffractive element730and first diffractive element720, converts left-hand circularly polarized beam722into a right-hand circularly polarized output beam732propagating parallel to the longitudinal direction (i.e., the z-axis). Polarization switch740is then utilized to transmit right-hand circularly polarized output beam732. Although polarization switch740is not required, the use of polarization switch740can improve the image quality. As will be evident to one of skill in the art, polarizing optics do not always result in the polarized light being in a single linear polarization state or in a single circularly polarized state. Rather, some light in undesired polarization states may be present after a polarizer or be introduced by polarizing optics, such as quarter wave plates, half wave plates, and the like. Moreover, although the diffraction efficiency of diffractive elements can be high, some input light can be diffracted in diffraction orders that are being suppressed or otherwise into undesired diffraction orders. As a result, various embodiments in accordance with the present disclosure utilize one or more polarization switches, for example polarization switch740illustrated inFIGS.7A and7Bto reduce or eliminate light in undesired polarization states. Thus, referring toFIG.2D, when either image220or225is intended to be generated, stray light present in one image will be prevented from being present in the other image.

FIG.7Billustrates a schematic diagram for the optical switch in a second operating condition in accordance with an embodiment of the present disclosure. In this second operating state, light beam760is input into optical switch700by passing through polarization rotator705. In this embodiment, polarization rotator705produces a left-hand circularly polarized beam to serve as light beam760. Light beam760has a width W. Since light beam760is a left-hand circularly polarized beam, if all diffracted orders other than the first positive diffracted order and the first negative diffracted order are suppressed, the handedness of the input light beam is changed to a right-hand circularly polarized beam and the output light beam is diffracted into the first negative diffracted order as a result of diffraction from first diffractive element720. Thus, first diffractive element720diffracts light beam760into the first negative diffracted order and converts light beam760into right-hand circularly polarized beam772, which is propagating at an angle −α. As discussed in relation toFIG.3, second diffractive element730is positioned a distance d, i.e., a longitudinal separation distance, from first diffractive element720and is aligned to be parallel to first diffractive element720. Second diffractive element730receives right-hand circularly polarized beam772propagating at angle −α. Second diffractive element730, which can be identical to first diffractive element720, thereby providing for the interchangeability of second diffractive element730and first diffractive element720, converts right-hand circularly polarized beam772into a left-hand circularly polarized output beam782propagating parallel to the longitudinal direction (i.e., the z-axis). Polarization switch740is then utilized to transmit left-hand circularly polarized output beam782. As discussed above, although polarization switch740is not required, the use of polarization switch740can reduce or eliminate light in undesired polarization states. In some embodiments, polarization switch740can be utilized to implement beam intensity control, modulating beam intensity. Thus, optical switch700can be utilized to not only control beam position, but beam intensity.

As illustrated inFIGS.7A and7B, the use of polarization rotator705in combination with first diffractive element720and second diffractive element730enables an optical switch that can be used to select between a first beam positioned at first location703and a second beam positioned at second location707. Thus, one of two spatially separated output light beams that are laterally separated from each other by separation distance s is produced by optical switch700. By using active polarization control implemented via control of polarization rotator705, the spatial separation functionality provided by the beam multiplication system can be utilized to select an output beam positioned at a predetermined location with respect to the input beam, enabling shifting of the image formed at the exit pupil of a laser beam scanning augmented reality system, for example, to correspond to the location of the pupil of the user's eye. In contrast with the beam multiplication system illustrated inFIG.3, which produces two output beams with equal intensity, optical switch700provides a single output beam (i.e., either right-hand circularly polarized output beam732positioned at first location703or left-hand circularly polarized output beam782positioned at second location707), which can approach 100% of the intensity of light beam710, thereby maintaining image intensity. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG.8Aillustrates a schematic diagram of another optical switch in a first operating condition in accordance with an embodiment of the present disclosure. Light beam810is input into optical switch800by passing through polarization rotator805. Polarization rotator805functions as a polarization switch to either maintain the polarization state of the light beam incident on polarization rotator805(i.e., operation in an “OFF” state) or to change the handedness of the light beam incident on polarization rotator805(i.e., operation in an “ON” state). In the embodiment illustrated inFIG.8A, polarization rotator805is operated in the “OFF” state and light beam810incident on polarization rotator805maintains the right-hand circularly polarized nature of light beam810.

Thus, light beam810is a right-hand circularly polarized beam after passing through polarization rotator805. Light beam810has a width W. Since light beam810is a right-hand circularly polarized beam, if all diffracted orders other than the first positive diffracted order and the first negative diffracted order are suppressed, the handedness of the input light beam is changed to a left-hand circularly polarized beam and the output light beam is diffracted into the first positive diffracted order. Thus, first diffractive element820diffracts light beam810into the first positive diffracted order and converts light beam810into left-hand circularly polarized beam822, which is propagating at an angle α. As discussed in relation toFIGS.3and7A, second diffractive element830is positioned a distance d, i.e., a longitudinal separation distance, from first diffractive element820and is aligned to be parallel to first diffractive element820. Second diffractive element830receives left-hand circularly polarized beam822propagating at angle α. Second diffractive element830, which can be identical to first diffractive element820, thereby providing for the interchangeability of second diffractive element830and first diffractive element820, converts left-hand circularly polarized beam822into a right-hand circularly polarized output beam832propagating parallel to the longitudinal direction (i.e., the z-axis).

FIG.8Billustrates a light beam present at a first location in the optical switch illustrated inFIG.8A. At first location801in the lateral plane, right-hand circularly polarized output beam832has been laterally shifted to the left with respect to the position of light beam810by a distance s/2. Thus, as illustrated inFIG.8B, image807is positioned on the left side of field of view809.

Polarization switch840is then utilized to either transmit right-hand circularly polarized output beam832as right-hand circularly polarized input beam837or to change the handedness of right-hand circularly polarized output beam832into a left-hand circularly polarized beam (not shown). As will be described more fully below, depending on the polarization state of the beam input into the second set of diffractive elements, i.e., third diffractive element850and fourth diffractive element860, the output beam generated by the second set of diffractive elements will either be located at a position in front of the plane of the image or behind the plane of the image.

In the embodiment illustrated inFIG.8A, polarization switch840is operated in an “OFF” state such that right-hand circularly polarized output beam832is transmitted through polarization switch840as right-hand circularly polarized input beam837. Right-hand circularly polarized input beam837is incident on third diffractive element850, which converts right-hand circularly polarized input beam837into left-hand circularly polarized beam852propagating at an angle α with respect to the x-axis (i.e., the first positive diffracted order m=+1 directed out of the plane of the figure). Since right-hand circularly polarized input beam837was collimated, left-hand circularly polarized beam852is also collimated.

A fourth diffractive element860is positioned a distance d from third diffractive element850and is aligned to be parallel to third diffractive element850. Fourth diffractive element860receives left-hand circularly polarized beam852, which is propagating at angle α lying in the x-z plane. Fourth diffractive element860, which can be identical to third diffractive element850, thereby providing for the interchangeability of fourth diffractive element860and third diffractive element850, converts left-hand circularly polarized beam852into a right-hand circularly polarized output beam862propagating parallel to the optical path.

FIG.8Cillustrates a light beam present at an output of the optical switch illustrated inFIG.8A. At second location803in the lateral plane, right-hand circularly polarized output beam862has been laterally shifted to a location in front of the plane of the figure by a distance s/2. Thus, as illustrated inFIG.8C, image808is positioned on the left, lower side of field of view809.

In another embodiment, polarization rotator805could be operated in the “ON” state and right-hand circularly polarized output beam832could be converted to a left-hand circularly polarized input beam that would replace right-hand circularly polarized input beam837and be received at the second set of diffractive elements as a left-hand circularly polarized input beam that would be deflected into the plane of the figure rather than out of the plane of the figure, i.e., diffracted into the first negative diffraction order m=−1 propagating in the x-z plane.

In this embodiment, the left-hand circularly polarized input beam would be incident on third diffractive element850, which would convert the left-hand circularly polarized input beam into a right-hand circularly polarized beam propagating at an angle −α with respect to the x-axis (i.e., the first negative diffracted order m=−1 directed into the plane of the figure). Fourth diffractive element860would then receive a right-hand circularly polarized beam and convert the right-hand circularly polarized beam into a left-hand circularly polarized output beam propagating parallel to the optical path. The left-hand circularly polarized output beam would form an image positioned on the left, upper side of field of view809.

FIG.9Aillustrates a schematic diagram of the optical switch illustrated inFIG.8Ain a second operating condition in accordance with an embodiment of the present disclosure. Light beam815, which is a left-hand circularly polarized beam, is input into optical switch800by passing through polarization rotator805. In the embodiment illustrated inFIG.9A, polarization rotator805is operated in the “ON” state and light beam815is converted into a right-hand circularly polarized beam872and diffracted into the first negative diffracted order propagating in the y-z plane as a result of diffraction from first diffractive element820. Thus, first diffractive element820diffracts light beam815into the first negative diffracted order and converts light beam815into right-hand circularly polarized beam872, which is propagating at an angle −α with respect to the y-axis. Second diffractive element830receives right-hand circularly polarized beam872propagating at angle −α and converts right-hand circularly polarized beam872into a left-hand circularly polarized output beam882propagating parallel to the longitudinal direction (i.e., the z-axis).

FIG.9Billustrates a light beam present at a first location in the optical switch illustrated inFIG.9A. At first location901in the lateral plane, left-hand circularly polarized output beam882has been laterally shifted to the right with respect to the position of light beam810by a distance s/2. Thus, as illustrated inFIG.9B, image907is positioned on the right side of field of view909.

Polarization switch840is then utilized to either transmit left-hand circularly polarized output beam882as left-hand circularly polarized input beam887or to change the handedness of left-hand circularly polarized output beam882into a right-hand circularly polarized beam (not shown). As will be described more fully below, depending on the polarization state of the beam input into the second set of diffractive elements, i.e., third diffractive element850and fourth diffractive element860, the output beam generated by the second set of diffractive elements will either be located at a position in front of the plane of the image or behind the plane of the image.

In the embodiment illustrated inFIG.9A, polarization switch840is operated in an “OFF” state such that left-hand circularly polarized output beam882is transmitted through the polarization switch as left-hand circularly polarized input beam887. Left-hand circularly polarized input beam887is incident on third diffractive element850, which converts left-hand circularly polarized input beam887into right-hand circularly polarized beam892propagating at an angle −α with respect to the x-axis (i.e., the first negative diffracted order m=−1 directed into the plane of the figure). Since left-hand circularly polarized input beam887was collimated, right-hand circularly polarized beam892is also collimated.

Fourth diffractive element860receives right-hand circularly polarized beam892, which is propagating at angle −α lying in the x-z plane. Fourth diffractive element860converts right-hand circularly polarized beam892into a left-hand circularly polarized output beam897propagating parallel to the optical path.

FIG.9Cillustrates a light beam present at an output of the optical switch illustrated inFIG.9A. At second location903in the lateral plane, left-hand circularly polarized output beam897has been laterally shifted to a location behind the plane of the figure by a distance s/2. Thus, as illustrated inFIG.9C, image908is positioned on the right, upper side of field of view909.

In another embodiment, polarization switch840could be operated in the “ON” state and left-hand circularly polarized output beam882could be converted to a right-hand circularly polarized input beam that would replace left-hand circularly polarized input beam887and be received at the second set of diffractive elements as a right-hand circularly polarized input beam that would be deflected out of the plane of the figure rather than into the plane of the figure, i.e., diffracted into the first positive diffraction order m=+1 propagating in the x-z plane.

In this embodiment, the right-hand circularly polarized input beam would be incident on third diffractive element850, which would convert the right-hand circularly polarized input beam into left-hand circularly polarized beam propagating at an angle +α with respect to the x-axis (i.e., the first positive diffracted order m=+1 directed out of the plane of the figure). Fourth diffractive element860would then receive a left-hand circularly polarized beam and convert the left-hand circularly polarized beam into a right-hand circularly polarized output beam propagating parallel to the optical path. The right-hand circularly polarized output beam would form an image positioned on the right, lower side of field of view909.

Thus, by operating polarization rotator805and polarization switch840in predetermined states, light beam810/815can be laterally shifted to one of four positions in a field of view in a controllable manner. In some embodiments, polarization switch840can be utilized to implement beam intensity control, modulating beam intensity. Thus, optical switch800can be utilized to not only control beam position, but beam intensity.

FIG.10Aillustrates a schematic diagram of an optical switch in a first operating condition in accordance with an embodiment of the present disclosure. Light beam1010is input into optical switch1000by passing through polarization rotator1005. Polarization rotator1005functions as a polarization switch to either maintain the polarization state of the light beam incident on polarization rotator1005(i.e., operation in an “OFF” state) or to change the handedness of the light beam incident on polarization rotator1005(i.e., operation in an “ON” state). In the embodiment illustrated inFIG.10A, polarization rotator1005is operated in the “OFF” state and light beam1010incident on polarization rotator1005maintains the right-hand circularly polarized nature of light beam1010.

First diffractive element1020diffracts light beam1010into the first positive diffracted order and converts light beam1010into a left-hand circularly polarized beam, which is propagating at an angle α with respect to the y-axis. The operation of first diffractive element1020is similar to that described with respect to the first diffractive element520illustrated inFIG.5. After diffraction from first diffractive element1020, polarization switch1025is used to either maintain the polarization state of the diffracted beam in the left-hand circularly polarized state or to convert the left-hand circularly polarized beam into a right-hand circularly polarized beam. Accordingly, third diffractive element1040operates in a manner similar to that described with respect to third diffractive element540inFIG.5, either converting the left-hand circularly polarized beam into a right-hand circularly polarized diffracted beam propagating at angle −α with respect to the x-axis or converting the right-hand circularly polarized beam into a left-hand circularly polarized diffracted beam propagating at angle +α with respect to the x-axis. In the embodiment illustrated inFIG.10A, polarization switch1025is operated in the “OFF” state, resulting in the generation of right-hand circularly polarized diffracted beam1032propagating at angle α with respect to the y-axis and angle −α with respect to the x-axis, i.e., angled to the left and into the plane of the figure.

In order to redirect the beam generated by diffraction of right-hand circularly polarized diffracted beam1032to propagate parallel to the optical path (i.e., along the z-direction), second diffractive element1030and fourth diffractive element1050are positioned a distance d from first diffractive element1020and third diffractive element1040. Diffraction by second diffractive element1030and fourth diffractive element1050also results in a change in the handedness of the beam incident on second diffractive element1030and fourth diffractive element1050.

In the embodiment illustrated inFIG.10A, since right-hand circularly polarized diffracted beam1032is present at location1003between the sets of diffractive elements, second diffractive element1030redirects the beam from propagation at angle α with respect to the y-axis to propagate along a direction aligned with the z-axis and converts right-hand circularly polarized diffracted beam1032to a left-hand circularly polarized diffracted beam. After diffraction from second diffractive element1030, polarization switch1045is used to either maintain the polarization state of the diffracted beam in the left-hand circularly polarized state or to convert the left-hand circularly polarized beam into a right-hand circularly polarized beam. In the embodiment illustrated inFIG.10A, polarization switch1045is operated in the “OFF” state, resulting in the left-hand circularly polarized diffracted beam being converted to right-hand hand circularly polarized output beam1052that is redirected from propagation at angle −α with respect to the x-axis to propagate along a direction aligned with the z-axis. After propagation through optical switch1000with both polarization switch1025and polarization switch1045operated in the “OFF” state, at second location1007in the lateral plane, right-hand circularly polarized output beam1052has been laterally shifted to the left by a distance s/2 and to a location behind the plane of the figure by a distance s/2. Thus, similar to right-hand circularly polarized output beam862as illustrated inFIG.8C, right-hand circularly polarized output beam1052would form an image positioned on the left, lower side of the field of view. Polarization switch1054can then be utilized to transmit right-hand circularly polarized output beam1052. Although polarization switch1054is not required, the use of polarization switch1054can improve the image quality by reducing or eliminating light in undesired polarization states.

FIG.10Billustrates a schematic diagram of the optical switch illustrated inFIG.10Ain a second operating condition in accordance with an embodiment of the present disclosure. A light beam is input into optical switch1000by passing through polarization rotator1005. In the embodiment illustrated inFIG.10B, polarization rotator1005is operated in the “ON” state and the light beam incident on polarization rotator1005is converted to a left-hand circularly polarized beam1060.

First diffractive element1020diffracts left-hand circularly polarized beam1060into the first negative diffracted order and converts left-hand circularly polarized beam1060into a right-hand circularly polarized beam, which is propagating at an angle −α with respect to the y-axis. After diffraction from first diffractive element1020, polarization switch1025is used to either maintain the polarization state of the diffracted beam in the right-hand circularly polarized state or to convert the right-hand circularly polarized beam into a left-hand circularly polarized beam. Accordingly, third diffractive element1040operates in a manner similar to that described with respect to third diffractive element540inFIG.5, either converting the right-hand circularly polarized beam into a left-hand circularly polarized diffracted beam propagating at angle α with respect to the x-axis or converting the left-hand circularly polarized beam into a right-hand circularly polarized diffracted beam propagating at angle −α with respect to the x-axis. In the embodiment illustrated inFIG.10A, polarization switch1025is operated in the “ON” state, resulting in the generation of right-hand circularly polarized diffracted beam1082propagating at angle −α with respect to the y-axis and angle +α with respect to the x-axis, i.e., angled to the right and out of the plane of the figure.

In order to redirect the beam generated by diffraction of right-hand circularly polarized diffracted beam1082to propagate parallel to the optical path (i.e., along the z-direction), second diffractive element1030and fourth diffractive element1050are positioned a distance d from first diffractive element1020and third diffractive element1040. Diffraction by second diffractive element1030and fourth diffractive element1050also results in a change in the handedness of the beam incident on second diffractive element1030and fourth diffractive element1050.

In the embodiment illustrated inFIG.10A, since right-hand circularly polarized diffracted beam1082is present at location1003between the sets of diffractive elements, second diffractive element1030redirects the beam from propagation at angle −α with respect to the y-axis to propagate along a direction aligned with the z-axis and converts right-hand circularly polarized diffracted beam1032to a left-hand circularly polarized diffracted beam. After diffraction from second diffractive element1030, polarization switch1045is used to either maintain the polarization state of the diffracted beam in the left-hand circularly polarized state or to convert the left-hand circularly polarized beam into a right-hand circularly polarized beam. In the embodiment illustrated inFIG.10B, polarization switch1045is operated in the “ON” state, resulting in the left-hand circularly polarized diffracted beam being converted to right-hand hand circularly polarized beam. The right-hand circularly polarized beam is then diffracted by fourth diffractive element1050to form left-hand circularly polarized output beam1092that is redirected from propagation at angle +α with respect to the x-axis to propagate along a direction aligned with the z-axis. After propagation through optical switch1000with both polarization switch1025and polarization switch1045operated in the “ON” state, at second location1007in the lateral plane, left-hand circularly polarized output beam1092has been laterally shifted to the right by a distance s/2 and to a location in front of the plane of the figure by a distance s/2. Polarization switch1054can then be utilized to transmit left-hand circularly polarized output beam1092. Although polarization switch1054is not required, the use of polarization switch1054can improve the image quality by reducing or eliminating light in undesired polarization states. In some embodiments, one or more of polarization switch1025, polarization switch1045, or polarization switch1054can be utilized to implement beam intensity control, modulating beam intensity. Thus, optical switch1000can be utilized to not only control beam position, but beam intensity.

FIG.11illustrates a schematic diagram demonstrating color separation during operation of a beam multiplication system in accordance with an embodiment of the present disclosure. As discussed above, the spectral content of the input light beam will impact the diffraction experienced passing through diffractive elements since diffractive effects are a function of wavelength. InFIG.11, red, green, and blue components of input beam1110are illustrated as diffracting at different angles for both the first positive diffracted order1122and the first negative diffracted order1124as input beam1110passes through and is diffracted by first diffractive element1120. Thus, red components diffract at a greater angle than blue components. After passing through and being diffracted by second diffractive element1130, the red, green, and blue components are propagating along the longitudinal axis aligned with the optical path and are characterized by a spatial separation from each other. Thus, not only are multiple beams produced as discussed in relation toFIG.3, but each of the output beams includes spectral components that are spatially separated.

Although color separation between the red, green, and blue components of input beam1110is illustrated inFIG.11, this is not required and the design of the diffractive elements, as well as the dimensions of the various optical components, can enable reductions of elimination of color separation effects. As an example, if color separation is occurring in a known manner, the diffractive elements can be modified, for example, separate recording of the holographic film for each color component, to compensate for the color separation. Moreover, the input beam could be adjusted, with different color components impinging on the diffractive elements at different angles of incidence or different divergence angles in order to pre-correct for spectrally dependent diffraction that will occur in the diffractive elements. It should be noted that in some embodiments, compensation for color separation is not utilized because the spatial separation between color components is a small fraction of the spatial separation between the light beams or angular information is maintained independent of the color separation. As an example, since the various embodiments according to the present disclosure will form an expanded eyebox with different image locations, the color components present in each image may result in slightly different size light beams for each color component. This may result in a slight white point variation, but this will most likely be a second order effect in comparison to the spatial separation between images.

FIG.12illustrates a schematic diagram of a transmissive beam multiplication system in accordance with another embodiment of the present disclosure. The transmissive beam multiplication system1200illustrated inFIG.12utilizes reflective polarization volume gratings to selectively reflect or transmit light depending on the polarization state of the light. As illustrated inFIG.12, projector1203can be utilized, with appropriate optical elements1207to couple input light from projector1203to impinge on transmissive beam multiplication system1200. Thus, transmissive beam multiplication system1200can be utilized in place of the other beam multiplication systems described herein as well as utilized as an element of the optical switches described herein.

As illustrated inFIG.12, projector1203and optical elements1207generate input light beam1210that is directed toward substrate1205. Substrate1205supports first reflective polarization volume grating1220and second reflective polarization volume grating1230. As described more fully below, each of first reflective polarization volume grating1220and second reflective polarization volume grating1230reflects light having a first polarization state and transmit light having a second polarization state.

Referring toFIG.12, input light beam1210is unpolarized. After passing through substrate1205, input light beam1210impinges on first reflective polarization volume grating1220. First reflective polarization volume grating1220reflects right-hand circularly polarized light to form right-hand circularly polarized reflected beam1242and transmits left-hand circularly polarized light to form left-hand circularly polarized transmitted beam1240. Second reflective polarization volume grating1230reflects right-hand circularly polarized reflected beam1242to form right-hand circularly polarized transmitted beam1246. Thus two output beams are formed using transmissive beam multiplication system1200: left-hand circularly polarized transmitted beam1240as a first output beam and right-hand circularly polarized transmitted beam1246as a second output beam.

The design of transmissive beam multiplication system1200, including the thickness of substrate1205, which impacts the lateral propagation distance for right-hand circularly polarized reflected beam1242along the y-direction between first reflective polarization volume grating1220and second reflective polarization volume grating1230, the lateral distance measured along the y-direction between first reflective polarization volume grating1220and second reflective polarization volume grating1230, and the input angle of input light beam1210, enables generation of output beams with a predetermined separation distance s between the output beams. Thus, transmissive beam multiplication system1200provides multiple output beams in a manner similar to beam multiplication system300illustrated inFIG.3.

In a manner similar to the cascading of multiple sets of diffractive elements as discussed in relation toFIG.4A, multiple transmissive beam multiplication systems can be cascaded to generate additional output beams. Thus, as illustrated inFIG.4, which shows the production of four output beams using a first set of diffractive elements producing two output beams laterally spaced apart from each other in the y-direction and a second set of diffractive elements introducing lateral spacing in the x-direction, multiple transmissive beam multiplication systems as illustrated inFIG.12can be cascaded with a quarter wave plate utilized between the transmissive beam multiplication systems to convert circularly polarized light into linearly polarized light in a manner similar to that discussed in relation to the operation of quarter wave plate435illustrated inFIG.4.

In some implementations and in order to provide multiple color operation, different reflective polarization volume gratings can be provided for each desired color, for example, three reflective polarization volume gratings each designed for operation with either red, green, or blue wavelengths, respectively. In some embodiments, the multiple reflective polarization volume gratings are formed as separate layers adjacent each other in place of first reflective polarization volume grating1220and second reflective polarization volume grating1230. Moreover, as discussed in relation to optical switch800illustrated inFIG.8AandFIG.9A, active polarization control elements can be utilized in conjunction with the multiple cascaded transmissive beam multiplication systems to generate a single output beam located at a predetermined position as illustrated inFIG.8CorFIG.9C. Thus, the discussion provided in relation to the optical switches described herein is applicable to systems utilizing transmissive beam multiplication systems as appropriate. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG.13illustrates a schematic diagram of a reflective beam multiplication system in accordance with an embodiment of the present disclosure. The reflective beam multiplication system1300illustrated inFIG.13utilizes reflective polarization volume gratings to selectively reflect light depending on the polarization state of the light. Although not illustrated inFIG.13for purposes of clarity, a projector as discussed herein can be utilized, with appropriate optical elements coupling input light from the projector to impinge on reflective beam multiplication system1300. Thus, reflective beam multiplication system1300can be utilized in place of the other beam multiplication systems described herein as well as utilized as an element of the optical switches described herein.

As illustrated inFIG.13, substrate1305supports first reflective polarization volume grating1307and substrate1315supports second reflective polarization volume grating1317. As described more fully below, each of first reflective polarization volume grating1307and second reflective polarization volume grating1317reflects light having a first polarization state.

Referring toFIG.13, input light beam1310is unpolarized. First reflective polarization volume grating1307is configured to reflect left-hand circularly polarized light and second reflective polarization volume grating1317is configured to reflect right-hand circularly polarized light. After impinging on first reflective polarization volume grating1307supported by substrate1305, input light beam1310is reflected by first reflective polarization volume grating1307to form left-hand circularly polarized output beam1320. The portion of input light beam1310that passes through first reflective polarization volume grating1307is incident on second reflective polarization volume grating1317supported by substrate1315. The light incident on second reflective polarization volume grating1317is reflected by second reflective polarization volume grating1317to form right-hand circularly polarized output beam1330. Thus two output beams are formed using reflective beam multiplication system1300: left-hand circularly polarized transmitted beam1320as a first output beam and right-hand circularly polarized transmitted beam1330as a second output beam.

The design of reflective beam multiplication system1300, including the thickness of substrate1305, which impacts the distance between first reflective polarization volume grating1307and second reflective polarization volume grating1317, and the input angle of input light beam1310, enables generation of output beams with a predetermined separation distance s between the output beams. Thus, reflective beam multiplication system1300provides multiple output beams in a manner similar to beam multiplication system300illustrated inFIG.3.

In a manner similar to the cascading of multiple sets of diffractive elements as discussed in relation toFIG.4A, multiple reflective beam multiplication systems can be cascaded to generate additional output beams. Thus, as illustrated inFIG.4, which shows the production of four output beams using a first set of diffractive elements producing two output beams laterally spaced apart from each other in the y-direction and a second set of diffractive elements introducing lateral spacing in the x-direction, multiple reflective beam multiplication systems as illustrated inFIG.13can be cascaded with a quarter wave plate utilized between the transmissive beam multiplication systems to convert circularly polarized light into linearly polarized light in a manner similar to that discussed in relation to the operation of quarter wave plate435illustrated inFIG.4.

FIG.14illustrates a schematic diagram of a laser beam scanning augmented reality system in accordance with an embodiment of the present disclosure. As illustrated inFIG.14, laser beam scanning augmented reality system1400includes a projector1410, which can be implemented as discussed in relation to projector110inFIG.1, and a beam shifting system1412. In some embodiments, beam shifting system1412is integrated as an element of projector1410, whereas in other embodiments, for example, when integrated with an eye-tracking system, beam shifting system1412can be implemented as a separate optical element, for example, as discussed in relation to beam multiplication system300inFIG.3, beam multiplication system400inFIG.4A, beam multiplication system500inFIG.5, optical switch700inFIGS.7A and7B, optical switch800inFIGS.8A and9, optical switch1000inFIGS.10A and10B. Laser beam scanning augmented reality system1400can also include projection optics1420operable to direct light produced using projector1410and/or beam shifting system1412toward a user.

Laser beam scanning augmented reality system1400additionally includes processor1430(e.g., a microprocessor), memory1432, and communications device1434.

Memory1432, also referred to as storage media, stores computer-readable instructions of an application, where the computer-readable instructions are executable by processor1430to run the application. Additional description related to these elements is provided more fully below.