Optical splitter

Abstract

The present disclosure relates to a light splitter for a scanning projector system such as provided in an augmented reality system, the light splitter having an input side and a spaced apart opposing output side, the input side having at least one input light facet and the output side having two or more output light facets, the at least one input light facet configured to receive an input light signal from a light source and the two or more output light facets arranged to output an output light signal in response to the input light signal, each output light facet defining an optical path, each optical path having a different refractive power.

Description

[Technical field]

[0001] The present disclosure relates to light splitters, and more particularly to light splitters for eyebox enlargement in virtual retinal display projector systems, such as augmented reality display systems. [Background technology]

[0002] Augmented reality (AR) displays, such as wearable (or head-mounted) displays, allow a user to view the external environment while also viewing the display content. The display content is an electronic message, such as a text message or instructional graphics, that is superimposed on the user's view of the external environment. The AR display allows a user to see what appears to be a traditional graphic display in the form of a virtual image floating in front of the user's field of view. The AR display may take the form of smart glasses, which may display the virtual image to a user wearing the smart glasses. Such AR display systems typically use holographic optical elements (HOEs) to direct light from a virtual retinal display projector to the user's eyes. The HOEs are typically provided in or on one or more lenses of the smart glasses.

[0003] In augmented reality displays, and more generally in optical devices used near the eye, such as telescopes or binoculars, the concept of an eyebox refers to the range of eye positions at which a user can see the image provided by the device or display. This concept is well known in the field of augmented reality displays and is described, for example, in U.S. Pat. No. 9,958,682, which discusses the relative advantages of providing a larger eyebox by pupil replication without adding bulky and expensive optics.

[0004] The light splitter described in U.S. Patent No. 9,958,682 uses multiple facets at the output of the light splitter, which works in conjunction with a holographic optical element to direct the multiple replicated pupils to the user's eye. However, a problem with this configuration is that the images sent to the multiple replicated pupils have different resolutions for each pupil, because the multiple replicated pupils result from a moving set of virtual projector beams that are not properly focused on the user's eye without additional optics.

[0005] To address this issue, it is known to use additional optical components such as liquid lenses. For the liquid lens solution to work properly, eye tracking is required to dynamically adjust the refractive power of the lens. The position of the user's pupil is detected and it is known that the ray path to the user's eye is due to one of multiple virtual projector positions. The refractive power of the lens is adjusted accordingly, improving the resolution for the particular replicated pupil used. Eye tracking is required to adjust the refractive power of the liquid lens and provide different refractive powers for each virtual projector position generated by the light splitter. Furthermore, liquid lenses are not optimal for correcting the aberrations of the projector system, since a single optical element is used to correct the aberrations of all replicated pupils. Summary of the Invention [Means for solving the problem]

[0006] Therefore, in light of the above, there is provided a light splitter for a scanning projector system, the light splitter comprising an input side and a spaced apart opposing output side, the input side including at least one input optical facet and the output side including two or more output optical facets, the at least one input facet arranged to receive an input optical signal from a light source, the two or more output facets arranged to output an output optical signal in response to the input optical signal, each output optical facet defining an optical path, each optical path having a different refractive power.

[0007] The two or more output optical facets each have a refractive power, and the refractive power of each of the at least two or more output facets is different. The output facets may be arranged in one dimension or may be arranged in two dimensions.

[0008] The optical power of each of the at least two or more output facets is defined by a radius of curvature of each of the output facets, each radius of curvature being different. The optical power of each of the at least two or more output facets is defined by a radius of curvature of each of the output facets, each output facet having a different center of curvature. The curvature of the output facets is at least one of concave and convex.

[0009] The input side includes two or more input optical facets, each of the two or more input facets having a respective refractive power, and the refractive power of each of the at least two or more input facets being different. The input facets are arranged in one dimension or arranged in two dimensions. The refractive power of each of the at least two or more input facets is defined by a radius of curvature of each of the input facets, each radius of curvature being different. The refractive power of each of the at least two or more input facets is defined by a radius of curvature of each of the input facets, each facet having a different center of curvature. The light splitter has a voluminous polygonal transparent structure, and the output optical facets each have a different focal length.

[0010] Also provided is a scanning projector system for a virtual retina display. The scanning projector system comprises a light source providing an input light signal, a scanning mirror arranged to reflectively scan the input light signal from the light source, and a light splitter according to an embodiment, the light splitter being arranged in an optical path of the scanning mirror, the scanning mirror being arranged to rotate between a first angular position and a second angular position. An input side of the light splitter is arranged to receive the input light signal reflectively scanned by the scanning mirror, and an output side of the light splitter is arranged to output an output light signal from one of the output facets depending on the angular position of the input light signal. The light source is an array of RGB light sources of laser diodes or light emitting diodes.

[0011] Also provided is a wearable virtual retinal display comprising a scanning projector system arranged to project a plurality of exit pupils onto the holographic optical element, the holographic optical element arranged to direct the plurality of exit pupils towards an eye of a user.

[0012] Further provided is an augmented reality eyeglasses with a virtual retinal display, the holographic optical element being disposed within or on the lens of the eyeglasses.

[0013] In order to allow the features of the present disclosure to be understood in detail, the present disclosure will be described more specifically with reference to the embodiments. Some of the embodiments are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings show only typical embodiments and are not intended to limit the scope of the present invention. The drawings are for ease of understanding the present disclosure and are not necessarily drawn to scale. The advantages of the claimed subject matter will be apparent to those skilled in the art upon reading the specification in conjunction with the accompanying drawings. In the accompanying drawings, like reference numerals are used to indicate like elements, as follows: [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a schematic diagram illustrating a light splitter according to an embodiment used in a scanning projector system. [Diagram 2] 2a, 2b, 2c, and 2d are top, end, and perspective views of an optical splitter according to an embodiment, respectively; [Diagram 3] 3a, 3b, and 3c are top, perspective, and perspective views of an optical splitter according to an embodiment; [Figure 4]4a, 4b, and 4c are top, perspective, and perspective views of an optical splitter according to an embodiment; [Figure 5a] FIG. 2 is a schematic diagram illustrating a light splitter according to an embodiment used in a scanning projector system. [Figure 5b] FIG. 5b is a ray diagram showing the output of the scanning projector system of FIG. 5a using a light splitter according to an embodiment together with a holographic optical element. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A scanning projector system 100 according to an embodiment is shown diagrammatically in FIG. 1. In overview, the scanning projector system 100 includes a light source 102, at least one scanning mirror 104, and a light splitter 106. The light source 102 may be any suitable light source, and may include, for example, an array of low-power RGB (red, green, blue) light sources, such as laser diodes or LEDs, that generate a collimated light beam. The collimated beam may have a beam diameter of, for example, about 1 mm, and the reflective surface area of ​​the at least one scanning mirror 104 may be determined accordingly. The light source 102 is disposed at the input side of the scanning mirror 104 to direct the light beam onto the scanning mirror 104. The light splitter 106 may be disposed at the output side of the scanning mirror 104 to receive the light beam reflected by the scanning mirror 104. The at least one scanning mirror 104 may be a two-dimensional scanning mirror, also known as a tip-tilt mirror. Alternatively, there may be two one-dimensional scanning mirrors, one scanning mirror scanning horizontally and the other scanning mirror scanning vertically. The scanning mirror may be any suitable micro-electromechanical system (MEMS) mirror. For simplicity and ease of explanation, the embodiments described herein show a two-dimensional type of scanning mirror, and those skilled in the art will appreciate that the inventive concepts of the present disclosure are equally applicable. The optical splitter 106 is disposed at the output side of the scanning mirror 104 and receives the light beam B (or input optical signal) from the light source 102 via the scanning mirror 104.

[0016] Optical splitter 106 is an optically transparent structure that receives an input light beam B from light source 102 at an input side 108 and refracts the input light beam B into a number of output beamlets B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15, B16, B17, B18, B19, B20, B210, B22, B23, B24, B25, B26, B27, B28, B29, B30, B31, B32, B33, B34, B35, B36, B37, B38, B39, B40, B41, B42, B43, B44, B45, B46, B47, B48, B49, B50, B51, B52, B53 n (or output optical signal). The optical splitter may be formed of spaced apart optically transparent structures or different separate adjacent optical structures.

[0017] The scanning mirror 104 is arranged to rotate over a range of rotation angles θ between a maximum and a minimum angular position. This range is known as the range of mechanical deflection of the scanning mirror. For example, the total range of rotation angles may be 30 degrees. In the illustrated example, the range of rotation angles is in a horizontal plane, but the description also applies to a vertical plane. If the scanning mirror 104 is a planar mirror surface, the maximum light reflection angle is twice the angle of the range of mechanical deflection angles that defines the range of the projection surface of the scanning mirror 104. Thus, the input light beam B may be scanned over the range of the projection surface of the scanning mirror 104.

[0018] An input side 108 of the optical splitter 106 is arranged to receive an input optical beam B from the scanning mirror 104 in the area of ​​a projection plane. The optical splitter 106 refracts the input optical beam B into a number of output beamlets B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15, B16, B17, B18, B19, B20, B21, B22, B23, B24, B25, B26, B27, B28, B29, B30, B31, B32, B33, B34, B35, B36, B37, B38, B39, B40, B41, B42, B43, B44, B45, B46, B47, B48, B49, B50, B51, B52, B53, B54, B55, B56, B57, B58, B59, B60, B61, B62, B63, B64, B65, B66, B67, B68, B69, B70, B71, B72, B73, B74, B75, B76, B77, B78, B79, B80, B81, B82, B83, B84, B85, B869, B90, B91, B92, B93, B94, B95, B96, B97, B98, B99, B100, B110, B120, B130, B140, B150, B161, B170, B182, B190, B103, B114, B115, B121, n These output beamlets exit the optical splitter 106 at the output side 110. In this manner, the optical splitter is disposed in the optical path of the scanning mirror. The output side 110 of the optical splitter 106 is provided with a number of output beamlets B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15, B16, B17, B18, B19, B20, B21, B22, B23, B24, B25, B26, B27, B28, B29, B30, B31, B32, B33, B34, B35, B36, B37, B38, B39, B40, B41, B42, B43, B44, B45, B46, B47, B48, B49, B50, B51, B52, B53, B54, B55, B56, B57, B58, B69, B60, B61, B62, B63, B64, B65, B66, B67, B68, B69, B70, B71, B72, B73, B74, B75, B76, B77, B78, B79, B80, B81, B82, B83, B84, B85, B86, B87, B88, B90, B91, B92, B93, B94, B95, B96, B97, B98, B99, B100, B99, B110, B99, B120, B99, B130, B99, B140, B99, B150, B99, B160, B99 n In the illustrated example, the three optical facets 112, 114, 116 split the input light beam B into respective output beamlets B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15, B16, B17, B18, B19, B20, B21, B22, B23, B24, B25, B26, B27, B28, B29, B30, B31, B32, B33, B34, B35, B36, B37, B38, B39, B40, B41, B42, B43, B44, B45, B46, B47, B48, B49, B50, B51, B52, B53, B54, B55, B56, B57, B58, B59, B60, B61, B62, B63, B64, B65, B66, B67, B68, B69, B70, B71, B72, B73, B74, B75, B76, B77, B78, B79, B80, B81, B82, B83, B84, B85, B86, B87, B88, B90, B91, B92, B93, B94, B95, B96, B97, B98, B99, B100, B110, B120, B130, B140, B150, B160, B170, B181, B190, B191, B202, B2103, B2204, B2305, B2406, B2507, B2 n However, the number of optical facets may be any positive integer n that splits the input beam B into a corresponding integer number n of output beamlets depending on the input angle of the input beam.

[0019] The eyebox of a scanning projector system, such as the scanning projector system 100 described above, is determined by the shape of the exit pupil from the projector. Such scanning projector systems typically use small exit pupils, typically on the order of 1 mm. 2 from 0.5 mm 2In an embodiment of projector system 100, to increase the size of the eyeboxes, the exit pupils are duplicated to increase the number of eyeboxes visible to the user, rather than increasing the size of a single eyebox. The advantage of this is that when the user's gaze deviates from the central eyebox location, the user's eyes move away from the central location, so that additional duplicated and spatially separated eyeboxes become visible to the user when the user's gaze deviates from the center. This concept is explained with reference to FIG. 5b below. The number of duplicated exit pupils, i.e. the number of spatially separated eyeboxes, is determined by the number of exit pupils that are duplicated, i.e. the number of spatially separated eyeboxes, depending on the number of output beamlets B. n , which corresponds to the number of optical facets at the output side 110 of the beam splitter 106.

[0020] Geometrically, the output beamlets B1, B2, and B n Each of the spatially separated virtual projector positions V1, V2, V n Specifically, optical splitter 106 splits or replicates input beam B into respective beamlets B1, B2, B n In this embodiment, output beamlet B1 is substantially emitted from virtual projector position V1. Output beamlet B2 is substantially emitted from virtual projector position V2, and output beamlet V n is effectively the virtual projector position V n The particular beamlets will depend on the angle at which the input beam B is scanned by the scanning mirror 104. In other words, the virtual projector positions V1, V2, V n are the beamlets B1, B2, and B n The beamlets B1, B2, and B n Each of these is focused onto an intermediate focal plane xx.

[0021] In use, optical splitter 106 receives an input optical beam B at input side 108. Optical beam B can be scanned by scanning mirror 104 through a total angular range θ, which corresponds to the range of available angles at which optical beam B may be incident on the input side of optical splitter 106. Based on the angle of incidence of optical beam B (as a subset of the total angular range θ), output beamlets from the optical splitter are designated B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15, B16, B17, B18, B19, B20, B21, B22, B23, B24, B25, B26, B27, B28, B29, B30, B31, B32, B33, B34, B35, B36, B37, B38, B39, B40, B41, B42, B43, B44, B45, B46, B47, B48, B49, B50, B51, B52, B53, B54, B55, B56, B67, B68, B69, B70, B71, B72, B73, B74, B75, B76, B77, B78, B79, B80, B81, B82, B83, B84, B85, B86, B87, B88, B90, B91, B92, B93, B94, B95, B96, B97, B98, B99, B100, B111, B121, B132, B142, B150, B161, B172, B183, B190, B104, B111, B1 n As the scanning mirror 104 scans the range θ, the beamlets B1, B2, B n gradually emerge from each output facet of the light splitter 106. In this way, the light splitter 106 replicates one eyebox at a time based on the scan angle of the scanning mirror 104. Those skilled in the art will appreciate that the scanning mirror scans a horizontal plane (the plane of the page as shown in FIG. 1) on the input side 108 of the light splitter 106. If the scanning mirror 104 is a two-dimensional scanning mirror, and the light splitter includes a two-dimensional array of facets, the scanning mirror is positioned to scan in the horizontal direction mentioned, as well as in a vertical direction (perpendicular to the plane of the page as shown in FIG. 1).

[0022] 2a, 2b, 2c, and 2d show schematic diagrams of a light splitter 206 according to an embodiment. In overview, the light splitter 206 has a generally voluminous polygonal structure having an input side and an opposing output side, where the input side 208 includes at least one optical facet and the output side 210 includes two or more adjacent output facets 212, 214, 216 that make up sides of the polygonal structure. For the embodiment of FIGS. 2a-2c, the input side 208 of the light splitter 206 includes a single planar input facet positioned to receive an input light beam from a scanning mirror over an angular rotation range θ and incouple the input light beam into the light splitter 206.

[0023] The output side 210 of the optical splitter 206 is a corresponding plurality of beamlets B1, B2, B3 split from the input light beam. n2a-2c, there are three output facets 212, 214, 216 arranged in a linear array. However, those skilled in the art will appreciate that there may be any number of output facets and they may be arranged in a two-dimensional n×m array (where n and m are positive integers, n=1 and m>2) or in a circular array. The number of output facets may be selected depending on the number and geometry of replicated eyeboxes required for a particular application. As mentioned above, each output optical facet is associated with a corresponding virtual projector position V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30, V31, V32, V33, V34, V35, V36, V37, V38, V39, V40, V41, V42, V43, V44, V45, V46, V47, V48, V49, V50, V51, V52, V53, V54, V55, V56, V57, V58, V59, V60, V61, V62, V63, V64, V65, V66, V67, V68, V69, V70, V71, V72, V73, V74, V75, V76, V77, V78, V79, V80, V81, V82, V83, V84, V85, V86, V87, V88, V89, V90, V91, V92, V93, V94, V95, V9 n , thereby defining a corresponding optical path through the optical splitter.

[0024] Two or more of the output light facets 212, 214, 216 may have or add refractive power, and in this regard, each of the output light facets 212, 214, 216 may have a curved surface that provides the refractive power. The configuration of the curved output facets 212, 214, 216 may provide a corresponding number of virtual projector positions V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30, V31, V32, V33, V34, V35, V36, V37, V38, V39, n A refractive power is introduced into the optical path defined by: The refractive powers of adjacent optical facets are different, and this difference results in a larger refractive power from one output optical facet to the adjacent output optical facet. Conversely, starting from the same optical facet, the difference may result in a smaller refractive power from one optical facet to the next.

[0025] In particular, the refractive power may increase from the first output light facet 212 to the second output light facet 214 and be maximum at the third output light facet 216. In the opposite case, the refractive power may decrease from the first output light facet 212 to the second output light facet 214 and be minimum at the third output light facet 216. As a non-limiting example of an increasing refractive power, the first output light facet may have a refractive power of +10 diopters (m -1 ), the second output optical facet has a refractive power of +30 diopters (m -1), and the third output optical facet has a refractive power of +100 diopters (m -1 ) may also be used. As a non-limiting example of a reduced power, the power of the first optical facet may be +100 diopters (m -1 ), the refractive power of the second optical facet is +30 diopters (m -1 ), the refractive power of the third optical facet is +10 diopters (m -1 ) In the above examples, a positive sign for the optical power is used to indicate a positive or convex curved optical facet surface (when considered in terms of the direction of light propagating through the light splitter), but one skilled in the art will appreciate that a negative sign for the optical power may be used to indicate a negative or concave curved optical facet surface (when considered in terms of the direction of light propagating through the light splitter).

[0026] Furthermore, the refractive power may vary and may be positive or negative for a beamlet depending on the specific nature of the input beam and application (e.g., augmented reality smart glasses) and the difference in refractive power that needs to be added / subtracted from the other beamlets. In fact, one skilled in the art will appreciate that any combination of convex, concave, curved or flat optical facet surfaces may be used such that the difference in refractive power is, for example, +40, +0, -40 diopters. The above-mentioned configuration examples and others also apply to output optical facets that are arranged in two dimensions, i.e., where there is a difference in refractive power between adjacent output optical facets.

[0027] One skilled in the art will understand that when applying a holographic optical element to AR, a larger positive focusing power is needed to move the intermediate focal plane xx closer to the light splitter and away from the holographic optical element. On the other hand, a larger negative refractive power is needed to move the intermediate focal plane xx closer to the holographic optical element and away from the light splitter. By appropriately selecting the difference in refractive power, the position of the intermediate focal plane can be matched to the position of the holographic optical element and can be adjusted to the shape of the eyebox, i.e., the spacing of the multiple replicated pupils in the eyebox (see FIG. 5b).

[0028] To achieve the appropriate refractive power difference, each output light facet may have a different radius of curvature. Optionally, each facet may have a different center of curvature (in other words, the inclination of the facet) relative to the incident beam and / or each facet may have both a different radius of curvature and a different center of curvature. The radius of curvature in this case is determined by the distance from the apex of the curvature of the respective facet to the center of curvature, where the apex is located on the optical axis of that facet. The above assumes that the refractive index is constant throughout the light splitter. In practice, each facet may be elliptical or may have a free curvature to allow further control of aberrations. Optionally, rather than different radii or centers of curvature, it may be possible to determine the required refractive power difference by utilizing a refractive index difference throughout the light splitter. This refractive index difference may be a graded index. In particular, the refractive index of the light splitter material is determined by the virtual projector positions V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30, V31, V32, V33, V34, V35, V36, V37, V38, V39, V40, V41, V42, V43, V44, V45, V46, V47, V48, V49, V50, V51, V52, V53, V54, V55, V56, V57, V58, V59, V60, V61, V62, V63, V64, V65, V66, V67 n , so that the corresponding virtual projector positions V1, V2, V n A difference in refractive power for each of the beamlets emitted from may be defined.

[0029] 2b and 2c show end and perspective views, respectively, of an output side 210 of a light splitter according to an example embodiment. In this example, the output side 210 is comprised of three facets 212, 214, 216 arranged in a 1×3 array. Those skilled in the art will appreciate that any number of facets may be provided on the output side 210 depending on the required number and location of pupil replicas. For example, as shown in the perspective view of FIG. 2d, if six pupil replicas are required, the output side 210 of the light splitter 206 may be arranged as a 2×3 array of output facets. Those skilled in the art will appreciate that the output light facets may thus be arranged as a two-dimensional n×m array, where n and m are positive integers, n>2 and m>2.

[0030] In the case of the 1×3 array shown in FIGS. 2a-2c, each facet may include an edge or end point that connects with the respective end points of adjacent facets. In this example embodiment, one end point of facet 212 will be adjacent to a first end point of facet 214. A second end point of facet 214 will be adjacent to an end point of facet 216, and this concept may be applied to any number of facets, such as the example 2×3 array of FIG. 2d. In this regard, the end point may not be a sharp line / boundary (particularly if adjacent facets have similar but not identical radii of curvature or similar but not identical centers of curvature) but may simply define an outer edge of the output facet at the output side that defines an intersection line between the facets that replicate separate and distinct pupils. In this regard, one skilled in the art will appreciate that each facet defines a separate and distinct eyebox (depending on the angle of incidence of input beam B at the input side of the light splitter, as discussed above).

[0031] Further, looking at the optical splitter shown in FIG. 2a, the individual output facets 212, 214, 216 may be concave, but the overall shape of the output surface 210 may also have a generally concave contour. Alternatively, the overall shape of the output surface may be generally convex, but still retain the facets 212, 214, 216 that are individually concave. The reverse is also true, the individual facets 212, 214, 216 may be convex, and the overall shape of the output surface 210 may also have a convex or concave contour. Furthermore, the individual output facets 212, 214, 216 may be at least one combination of concave, convex, and flat, and the overall shape of the output surface 210 may also have a convex or concave contour, regardless of the individual curvature of the output facets.

[0032] 3a and 3b show schematic diagrams of a light splitter 306 according to an embodiment. In overview, the light splitter 306 has a generally voluminous polygonal structure having an input side and an output side, the input side 308 and the output side 310 having a generally faceted structure constituting the sides of the polygonal structure. The output side 310 may be a configuration consistent with the configuration of Figs. 2a-2c or the configuration of Fig. 2d described above. Unlike the arrangement of Figs. 2a-2c, for the configuration of Figs. 3a and 3b, the input side 308 includes a curved input facet arranged to receive an input light beam from the scanning mirror over a range of angular rotation θ and in-couple the input light beam into the light splitter 306. The input side may be circularly, elliptically, or freeform curved to provide optical power, and may be concave or convex. Similar to the arrangement of FIG. 2d described above, the output light facets of the output side 310 may be arranged in a two-dimensional n×m array as shown in FIG. 3c.

[0033] 4a and 4b show schematic diagrams of an optical splitter 406 according to an embodiment. In overview, the optical splitter 406 has a generally voluminous polygonal structure having an input side and an output side, the input sides 408 and 410 of which have a generally faceted structure constituting the sides of the polygonal structure. The output side 410 may have a configuration consistent with the configuration of FIGS. 2a-2c described above. Unlike the configuration of FIGS. 2a-2c, in the embodiment of FIGS. 4a and 4b, the input side 408 may include a number of curved input facets 418, 420, 422 arranged to receive an input light beam from a scanning mirror over a range of angular rotation θ and in-couple the input light beam into the optical splitter 406. The input facets may be arranged as an n×m array, where n and m are positive integers, and n=1 and m>2, or n>1 and m>2. Each input facet may be curved circularly, elliptically, or freeform. Those skilled in the art will appreciate that the input optical facets may be arranged in a similar manner as the facets of the output side 410, i.e., the input facets may be arranged as an array of facets, each of which may have a refractive power, and the facets may be individually concave or convex such that each has a different refractive power. The input surface may define an overall contoured convex or concave shape, regardless of the individual curvatures of the input facets 418, 420, 422. Similar to the configurations of Figures 2d and 3b above, the output optical facets of the output side 410 may be arranged as a two-dimensional n x m array as shown in Figure 4c.

[0034] Thus, according to the above description, the input and output optical facets can be considered as thin lens surfaces working in close proximity to each other, with the refractive power of such lens surfaces being equal to the sum of the refractive powers of each surface. The input and output optical facets can be considered to cooperate when they share an optical path defined by a virtual projector position. More specifically, for the embodiment of Figures 3a-3c having a curved input side, the total refractive power P associated with each of the output facets 312, 314, 316 is Total is the optical power P of each individual output facetout and the refractive power of the curved input side P in 1, the refractive power associated with virtual projector V1 and beamlet B1 is equal to the refractive power of input side 108 and output facet 112. This also applies to the refractive power associated with virtual projector V2 and beamlet B2 for output facet 114, and so on for each virtual projector V2 and beamlet B2 for a particular output facet. n , Beamlet B n Similarly, for the embodiment of Figures 4a-4c having curved facet inputs, the total optical power P associated with each of the output facets 412, 414, 416 is Total is the optical power P of each individual output facet out and the optical power P of each of the input facets 418, 420, 422. in In other words, as in the example of FIG. 1, the refractive power associated with virtual projector V1 and beamlet B1 is equal to the refractive power of the input facet and the respective output facet. This also applies to the refractive power associated with virtual projector V2 and beamlet B2, each for a respective pair of input and output facets, and so on for each virtual projector V2 and beamlet B2 for a particular pair of input and output facets. n , Beamlet B n The same applies to each of the above.

[0035] According to an embodiment, the optical splitters 106, 206, 306, 406 may be formed of any suitable optical material, such as optical glass (e.g., BK-7), acrylic, or fluorite. The maximum thickness of the optical splitter (from input side to output side) is in the range of a few millimeters (mm) and typically 2-10 mm, preferably about 3-5 mm. The optical splitter may have an air gap between the input side and the output side. The optical splitter may be formed of a combination of optical materials, where the input side is formed of one material and the output side is formed of another material. Similarly, the input side may be formed of the same material as the output side, but with a different index of refraction.

[0036] By applying optical powers to the light splitter as described herein, the replicated pupils result from a series of moving positions (such as virtual projector positions) that are properly focused on the user's eye, resulting in uniform image quality across eyeboxes, thereby improving resolution. Additionally, these optical powers can be selected to correct for specific aberrations in the eyeboxes, improving resolution. Such improvements are possible without the use of liquid lenses and their associated problems.

[0037] Light splitters 206, 306, 406 of the type described above with respect to Figures 2a-2d, 3a-3c, and 4a-4c may be included in a scanning projector system of the type shown in Figure 1. Figure 5a shows a scanning projector system using a light splitter 306 of the type described above with respect to Figures 3a and 3b. Those skilled in the art will appreciate that any of the light splitters described herein may be used depending on the particular circumstances of the application and consistent with the inventive concepts described. If the input and / or output facets are a two-dimensional array with more than two facets in each direction of the array (e.g., 3x3, etc.), the scanning mirror may be a two-dimensional scanning mirror. The number of facets on the input side may be equal to the number of optical facets on the output side. Conversely, the number of facets on the input side may not be equal to the number of optical facets on the output side.

[0038] 1, light from a light source 502 is reflected by a scanning mirror 504 to an input side 308 of a light splitter 306. An output side 310 of the light splitter 306, which includes multiple output facets 312, 314, 316, provides a corresponding number of output beamlets B1, B2, B3 from an input light beam B. n The optical splitter 306 is positioned to outcouple the input beam B from the output beamlets B1, B2, and B3 depending on the angle of incidence of the input beam B at the input side of the optical splitter 306. n This is done by out-coupling one of the virtual projector positions V1, V2, and V nSpecifically, when scanning mirror 504 is at a first angle corresponding to virtual projector position V1, output beamlet B1 emerges from optical facet 312 on output side 310 of light splitter 306. Similarly, when scanning mirror 504 is at a first angle corresponding to virtual projector position V2 or V n , then output beamlet B2 or B3 will be emitted from optical facet 314 or 316 of output side 310 of optical splitter 306 depending on the angle of input beam B. n The output beamlet B1 is focused to an intermediate focus f1 due to the refractive power associated with the input and output facets 312. Similarly, the output beamlet B2 is focused to an intermediate focus f2 due to the refractive power associated with the input and output facets 314. Furthermore, the output beamlet B n is the intermediate focus f due to the optical power associated with the input and output facets 316. n The focal length f1 of beamlet B1 emerging from output facet 312 may be smaller than the focal length f2 of beamlet B2 emerging from output facet 314. The focal length f2 of beamlet B2 emerging from output facet 314 may be smaller than the focal length f2 of beamlet B2 emerging from output facet 316. n The focal length f n In other words, f1 <f2<f n Alternatively, depending on the particular application, the focal length f1 of the beamlet B1 emerging from the output facet 312 may be greater than the focal length f2 of the beamlet B2 emerging from the output facet 314. The focal length f2 of the beamlet B2 emerging from the output facet 314 may be greater than the focal length f2 of the beamlet B2 emerging from the output facet 316. n The focal length f n In other words, f1>f2>f n Thus, the focal length either monotonically increases or monotonically decreases from one facet to the next.

[0039] Following the above example, if the first output optical facet has a refractive power of +10 diopters, the second output optical facet has a refractive power of +30 diopters, and the third output optical facet has a refractive power of +100 diopters, the corresponding focal lengths are 10 mm, 30 mm, and 100 mm, respectively (note that FIG. 5a is not drawn to scale). Thus, depending on the incident input beam, each output beam will have a net refractive power difference. As a result, the focus of the intermediate focal plane can be shifted by an amount depending on the refractive power experienced by the beamlet passing through one of the output optical facets. In this way, the light splitter can be optimized for a particular holographic optical element design and eyebox replication shape without the need for additional optical components, e.g., liquid lenses. For example, without the use of refractive power, one beamlet may have a focal length of 40 mm (from the holographic optical element). At 4 diopters, the focus shift may be approximately 5 mm.

[0040] Thus, as one skilled in the art will appreciate, the refractive power determined by the combination of the input refractive power (which may be zero in the configurations of Figs. 2a-2d) and the refractive power of the output facet allows the focal length of a particular beamlet to be changed depending on the angle of incidence of the input beam at the light splitter. This improves the collimation of the beamlets to the respective eyeboxes, even without a liquid lens. This has a clear advantage over known solutions such as liquid lenses, since no expensive and complex control electronics are required to adjust the focal length of the liquid lens depending on the angle of the beamlet incident on the liquid lens.

[0041] With reference to FIG. 1 and FIG. 5a including the light splitter according to the embodiment, the scanning projector system of the type described above may be used in augmented reality (AR) systems, such as smart glasses, head-mounted displays, and head-up displays. AR systems are well known in the art and typically include a scanning projector system, which when in use projects an image onto a holographic optical element (HOE), from which the image is sent to the user's eye. The HOE may be located within or on a lens of the AR system, which may be mounted in a frame, such as an eyeglass frame. The frame may also support a projector system, which may be mounted or housed in the frame, such as an arm of the eyeglass frame. The projector may be aligned with the lens, including the HOE, to direct an image to the user's eye.

[0042] Output beamlets B1, B2, B3 from a projector system according to an embodiment n A schematic diagram showing how beamlet B enters the holographic optical element (HOE) is shown in FIG. 5b (not drawn to scale, as is FIG. 5a). Depending on the input angle of input light beam B from light source 502 and scanning mirror 504 shown in FIG. 5a, spatially separated exit pupils 510, 520, and 50n are projected onto the user's eye. When scanning mirror 504 is in a position corresponding to virtual projector point V1, beamlet B1 exits the light splitter at facet 312 and focuses to focal point f1. Beamlet B1 then enters the holographic optical element (HOE) and is directed to exit pupil position 510. Similarly, when scanning mirror 504 is in a position corresponding to virtual projector point V2, beamlet B2 exits the light splitter at facet 314 and focuses to focal point f2. Beamlet B2 then enters the holographic optical element (HOE) and is directed to exit pupil position 520. Similarly, the scanning mirror 504 is aligned with the virtual projector point V n When beamlet B is at a position corresponding to n exits the light splitter at facet 316 and reaches a focal point f n Then, beamlet B nenters the holographic optical element (HOE) and is directed to the location of the exit pupil 50n. Due to the different refractive power experienced by each beamlet, these beamlets are focused at different focal lengths from the light splitter. In other words, each output facet of the light splitter has a different focal length. In this way, based on the input angle of the input light beam B, a pupil duplication in the user's eye can be achieved without reducing the image resolution and without the need for additional optical elements such as liquid lenses and the associated problems.

[0043] It should be noted that the curvature of the optical facets shown in the accompanying drawings has been exaggerated for illustrative purposes and is not intended to be inferred to scale (unless stated in the text or drawings).

[0044] Particular preferred aspects of the present disclosure are set out in the independent claims. Combinations of features from the dependent and / or independent claims may be combined as appropriate and not just as set out in the claims.

[0045] The scope of the present disclosure includes any novel feature or combination of features, explicitly or implicitly disclosed, or generalization thereof, whether or not relevant to the present disclosure or whether or not it alleviates any or all of the problems addressed by the present disclosure. The applicant hereby states that new claims may be formulated to such features during prosecution of this application or any application derived therefrom. In particular, with reference to the claims, the features of the dependent claims may be combined with the features of the independent claims, and the features of each independent claim may be combined in any suitable manner and not only in the specific combinations recited in the claims.

[0046] Features that are described in the context of separate embodiments can also be combined in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment can also be provided separately or in any suitable subcombination.

[0047] The word "comprising" does not exclude other elements or steps and the word "a" or "an" does not exclude a plurality. Reference signs in the claims do not limit the scope of the claims.

Claims

1. 1. An optical splitter for a scanning projector system, comprising: The optical splitter comprises: The input side, an output side facing each other at a distance; Equipped with the input side includes at least one input optical facet; the output side includes two or more output optical facets; the at least one input facet is positioned to receive an input optical signal from a light source; the two or more output facets are arranged to output an output optical signal in response to the input optical signal; each said output facet defines an optical path; Each of the optical paths has a different refractive power. Optical splitter.

2. 2. The optical splitter of claim 1, each of the two or more output optical facets having a respective optical power; the optical power of each of the at least two or more output facets is different; Optical splitter.

3. 3. The optical splitter according to claim 1, the output facets are arranged in one dimension; Optical splitter.

4. 3. The optical splitter according to claim 1, the output facets are arranged in two dimensions; Optical splitter.

5. An optical splitter according to any one or more of claims 1 to 4, the optical power of each of the at least two or more output facets is defined by a radius of curvature of each of the output facets; each said radius of curvature is different; Optical splitter.

6. An optical splitter according to any one or more of claims 1 to 5, the optical power of each of the at least two or more output facets is defined by a radius of curvature of each of the output facets; Each of the facets has a different center of curvature. Optical splitter.

7. 7. An optical splitter according to claims 5 and 6, the curvature of the output facet is at least one of concave and convex; Optical splitter.

8. 8. The optical splitter according to claim 1, the input side includes two or more input optical facets; Optical splitter.

9. 9. The optical splitter of claim 8, each of the two or more input optical facets having a respective optical power; Optical splitter.

10. 10. The optical splitter of claim 9, the optical power of each of the at least two or more input facets is different; Optical splitter.

11. 9. The optical splitter of claim 8, the input light facets are arranged in one dimension; Optical splitter.

12. 9. The optical splitter of claim 8, the input light facets are arranged in two dimensions; Optical splitter.

13. 9. The optical splitter of claim 8, the optical power of each of the at least two or more input facets is defined by a radius of curvature of each of the input facets; each said radius of curvature is different; Optical splitter.

14. 9. The optical splitter of claim 8, the optical power of each of the at least two or more input facets is defined by a radius of curvature of each of the input facets; Each of the facets has a different center of curvature. Optical splitter.

15. An optical splitter according to any one of claims 1 to 14, It has a voluminous polygonal transparent structure, Optical splitter.

16. 2. The optical splitter of claim 1, each of said output light facets having a different focal length; Optical splitter.

17. 1. A scanning projector system for virtual retinal display, comprising: The scanning projector system includes: a light source for providing an input optical signal; a scanning mirror arranged to reflectively scan the input optical signal from the light source; An optical splitter according to any one of claims 1 to 15, Equipped with the optical splitter is disposed in an optical path of the scanning mirror; the scanning mirror is arranged to rotate between a first angular position and a second angular position; Scanning projector system.

18. 20. The scanning projector system of claim 17, the input side of the optical splitter is positioned to receive the input optical signal reflectively scanned by the scanning mirror; the output side of the optical splitter is arranged to output an output optical signal from one of the output optical facets depending on the angular position of the input optical signal. Scanning projector system.

19. 20. The scanning projector system of claim 17, The light source is an array of RGB light sources of laser diodes or light emitting diodes. Scanning projector system.

20. 1. A virtual retinal display, comprising: A scanning projector system according to any one of claims 16 to 19; A holographic optical element; Equipped with the scanning projector system is positioned to project a plurality of exit pupils onto the holographic optical element; the holographic optical element is positioned to direct the plurality of exit pupils toward a user's eye; Virtual retina display.

21. Augmented reality glasses comprising the virtual retinal display of claim 20, The holographic optical element is disposed within or on a lens of the eyeglasses. Augmented reality glasses.

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