Spectacle lens having a waveguide

Abstract

The present disclosure relates to an augmented reality eyeglass lens having a waveguide and a method of manufacturing such eyeglass lens having a waveguide, the eyeglass lens comprising: a first lens portion and a second lens portion and a cylindrical waveguide therebetween, the cylindrical waveguide having cylindrical concentric opposed surfaces defining a first cylindrical interface with the first lens portion and a second cylindrical interface with the second lens portion, the cylindrical waveguide being transparent and including a central waveguide core having a transparent medium at the first and second cylindrical interfaces.

Description

[Technical field]

[0001] The present disclosure relates to eyeglass lenses with waveguides for augmented reality displays and methods of manufacturing such eyeglass lenses with waveguides. [Background technology]

[0002] In the field of Augmented Reality (AR), a user is presented with a virtual image overlaid on the real world using a transparent combiner that redirects the image from a projector system to the user's eye. Current solutions typically use a planar transparent waveguide made of glass or plastic material, where light from a projector is in-coupled into the waveguide via a diffraction grating, traverses along the length of the waveguide by total internal reflection, and out-coupled to the user's eye by a further diffraction grating. In such applications, the thickness of the waveguide is typically a few millimeters (mm).

[0003] Transparent combiner solutions based on free-space reflective optics exist, but these typically have a small area (also known as the eyebox) where such an image or array of images is visible by the user. Therefore, free-space reflective optics are not suitable for applications where a large eyebox is required. A small eyebox area requires the AR glasses to be mechanically adjusted or adapted to a specific user due to differences in interpupillary distance (IPD), thus increasing cost and complexity. On the other hand, solutions based on planar waveguides have a large eyebox area, which means that a single variation of the AR glasses design can fit most user populations and users can easily see the virtual image.

[0004] It is known to embed the above-mentioned type of waveguides in eyeglass lenses, which is desirable for many reasons. Specifically, in AR applications, the input and output coupling gratings can be holographic optical elements (HOEs) with a thickness of less than 1 millimeter (mm). However, embedding such waveguides in lenses has limitations. Typically, the lenses used in eyeglasses are curved, especially if the lenses are prescription lenses, while the waveguides are flat. Thus, embedding a waveguide in a curved lens has the disadvantage that the thickness of the lens must be large to accommodate the flat waveguide, and therefore heavier.

[0005] There are several approaches to encapsulate thin films within lenses or to laminate thin films onto eyeglasses. Such approaches may be useful for incorporating HOEs less than a millimeter thick, but are not suitable for use with millimeter thick waveguides encapsulated within eyeglass lenses. Furthermore, none of the known solutions consider the problems associated with achieving the necessary refractive index changes within eyeglass lenses to ensure that light rays can be efficiently directed from the light source to the user's eye to continuously replicate the pupil without diverging light rays from the same image pixel when projected at infinity. Summary of the Invention

[0006] A spectacle lens for an augmented reality display is provided, the spectacle lens comprising a first lens portion and a second lens portion and a cylindrical waveguide therebetween, the cylindrical waveguide having cylindrical, concentric, opposed surfaces defining a first cylindrical interface with the first lens portion and a second cylindrical interface with the second lens portion, the cylindrical waveguide being transparent and including a central waveguide core having a transparent medium at the first and second cylindrical interfaces.

[0007] The central core may have a higher refractive index than the transparent medium, which is an adhesive material or an air gap. The first lens portion, the second lens portion, the cylindrical waveguide, and the transparent medium are arranged as an optical stack.

[0008] The spectacle lens may have a major axis and a minor axis, and the first and second cylindrical interfaces may have a curved profile along the major axis. The first and second cylindrical interfaces may have a linear profile along the minor axis. The first lens portion and the second lens portion have a spherical outer profile.

[0009] The eyeglass lens may further comprise input optics, the input optics constructed and arranged to couple light into the cylindrical waveguide. The input optics may include an input coupling linear grating having a fixed period applied to a surface of the waveguide. The input coupling linear grating may be attached to the waveguide at the first cylindrical interface or the second cylindrical interface. The input coupling linear grating may be switchable. The input coupling linear grating may be formed of a holographic material.

[0010] The input optics are constructed and arranged to receive light rays from the image source and direct the light rays into the cylindrical waveguide such that all light rays emanating from the same pixel of the image source are incident on the surface of the cylindrical waveguide at each point of incidence at the same angle relative to a surface normal to the common cylindrical axis and at the same angle relative to a plane normal to the common cylindrical axis, such that the coupled-in light may retain its directional angle as it propagates along the cylindrical waveguide.

[0011] The eyeglass lens may further comprise output optics constructed and arranged to receive the propagated light from the cylindrical waveguide and present the light as an image to the user's eye. The output optics may include an output coupling linear grating having a fixed period applied to a surface of the waveguide. The output coupling linear grating may be attached to the waveguide at the first cylindrical interface or the second cylindrical interface. The output coupling linear grating may be switchable. The output coupling linear grating may be formed of a holographic material. The output coupling linear grating may be attached to the waveguide at the first cylindrical interface or the second cylindrical interface.

[0012] Also provided is a method of manufacturing a eyeglass lens for an augmented reality display, the method including forming a first lens portion and a second lens portion and inserting a cylindrical waveguide therebetween, and forming a cylindrical waveguide having cylindrical, concentric, opposed surfaces defining a first cylindrical interface with the first lens portion and a second cylindrical interface with the second lens portion, the cylindrical waveguide being transparent and including a central waveguide core having a transparent medium at the first and second cylindrical interfaces.

[0013] The central core may have a higher refractive index than the transparent medium. The transparent medium may be an adhesive material. The transparent medium may be an air gap. The first lens portion, the second lens portion, the cylindrical waveguide, and the transparent medium may be arranged as an optical stack.

[0014] Thus, advantageously, eyeglass lenses for augmented reality displays are encapsulated with a curved waveguide within the lens, which provides a replicated eyebox with substantially reduced aberrations.

[0015] In order to allow the features of the present disclosure to be understood in detail, a more detailed description will be made with reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only typical embodiments and are therefore not considered to be limiting of its scope. The drawings are for ease of understanding of the present disclosure and therefore are not necessarily drawn to scale. The advantages of the claimed subject matter will be apparent to those skilled in the art upon reading this description in conjunction with the accompanying drawings. In the accompanying drawings, like reference numerals are used to designate like elements. [Brief description of the drawings]

[0016] [Figure 1a] 1A and 1B illustrate diagrammatically a perspective view of a spectacle lens having a waveguide according to an embodiment; [Figure 1b] 1A and 1B illustrate diagrammatically an exploded top-down view of a spectacle lens having a waveguide, according to an embodiment; [Figure 1c]1A and 1B illustrate a side view of a spectacle lens having a waveguide according to an embodiment. [Diagram 2] 1 illustrates a schematic diagram of a waveguide for a spectacle lens, according to an embodiment. [Diagram 3] 1 illustrates a schematic input coupling optics for a waveguide of a spectacle lens, according to an embodiment. [Figure 4] 1 illustrates schematic input and output coupling optics for a waveguide of an eyeglass lens, according to an embodiment. [Diagram 5] 1 illustrates a schematic diagram of a light source, input and output coupling optics, and a user's eye relative to a waveguide in a spectacle lens, according to an embodiment. [Figure 6] 1 illustrates a schematic output coupling optics for a waveguide of an eyeglass lens, according to an embodiment. [Figure 7a] 1A and 1B illustrate diagrammatically a perspective view of a spectacle lens having a waveguide according to an embodiment; [Figure 7b] 1A and 1B illustrate diagrammatically an exploded top-down view of a spectacle lens having a waveguide, according to an embodiment; [Figure 7c] 1A and 1B illustrate a side view of a spectacle lens having a waveguide according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] 1a-1c, a spectacle lens 100 according to an embodiment comprises a first lens portion 102, a second lens portion 104 (also known as a first lens half and a second lens half, respectively), and a waveguide 106 (also known as a light guide) interposed between the first lens portion 102 and the second lens portion 104. In this manner, the first and second lens portions 102, 104 and the waveguide 106 are arranged as an optical stack. The waveguide 106 has first and second opposing surfaces designated as an eye-facing surface and a world-facing surface, respectively. Similarly, the first lens portion 102 is designated as a world-facing lens since it is on the side of the waveguide 106 that faces the world during use. The second lens portion 104 is designated as an eye-facing lens since it is on the side of the waveguide that faces the user's eye during use. The stacked arrangement of lens portions 102 , 104 and waveguide 106 is transparent to the real world, i.e., a user can see the world through the eyeglass lens 100 .

[0018] A waveguide 106 of the type utilized in the eyeglass lens 100 is illustrated diagrammatically in FIG. 2, with lens portions 102, 104 omitted for clarity, but their positions shown for reference. The waveguide 106 is cylindrical in shape, with first and second concentric opposing surfaces 108, 110, with a constant thickness t between the opposing surfaces 108, 110. The center of curvature of the waveguide 106 is designated as X. The distances designated R1 and R2 are the radii of curvature between the center of curvature and the respective opposing concentric circular surfaces 108, 110. In this manner, the concave side of the cylindrical waveguide 106 is seen to face the eye, as will be discussed in more detail below. Similarly, the distance from the center of curvature X to the inner or eye-facing surface 110 of the waveguide 106 is R1, and the distance from the center of curvature X to the outer (world-facing) surface 108 of the waveguide 106 is R2. It is clear that R2=R1+t, and for the constant thickness t, this applies regardless of where on the cylindrical waveguide 106 the distances R1 and R2 are measured. In other words, the waveguide 106 has a common center of curvature X, and the radii R1 and R2 of the inner surface 110 and outer surface 108 of the waveguide 106 are separated by the constant thickness t.

[0019] 1a and 1b, an input coupling grating 132 may be provided on a surface of the waveguide 106 to input light from a light source into the waveguide 106. A corresponding output coupling grating 134 may be provided on a surface of the waveguide to output light from the waveguide to a user's eye. The input coupling grating 132 and the output coupling grating 134 may be positioned on the waveguide 106 such that the waveguide 106 lies within the footprints of the first and second lens portions when the waveguide 106 is fixed to a surface on concentric opposite sides of the waveguide 106.

[0020] Using such a structured cylindrical waveguide 106 may allow light to travel between curved surfaces without aberration. This is advantageously implemented with input optics, such as lenses, prisms, mirrors, arranged to receive light from an image source (particularly a pixelated image source or an image source having a light output that can at least conceptually be divided into pixels) and provide light to the cylindrical waveguide 106. All light rays from the same pixel of the image source enter the cylindrical waveguide 106 at the same angle relative to the plane of incidence normal at each point of incidence. Thus, all light from the central pixel of the image source enters at any point on the cylindrical waveguide 106 that is perpendicular to the cylindrical surface. Light rays from non-central pixels enter at the same angle relative to the surface normal at each point of incidence. Furthermore, all light rays from the same pixel of the image source enter the cylindrical waveguide 106 at the same angle relative to the plane perpendicular to the cylinder axis at each point of incidence. Thus, the propagation direction of all light rays remains the same.

[0021] Considering the input optics illustrated in Figure 3 and the waveguide structure described above, light received at the cylindrical waveguide (typically in-coupled into the cylindrical waveguide) retains its orientation angle as it propagates along the cylindrical waveguide. That is, all light rays from a given pixel, no matter how far they propagate, approach the output grating at the same angle measured between the light rays and the surface at the point of incidence of each light ray. Typically, the input optics includes in-coupling (or injection) optics.

[0022] Unlike conventional collimating optics used for planar waveguides, the input optics proposed in this disclosure are not properly called collimators in classical optical design terminology, since the light rays from the pixels are not parallel. Rather, the preferred input coupling (projector) optics includes optical devices arranged to collimate or align (only) the light passing through (i.e., neither parallel nor completely including), more preferably in a plane perpendicular to the cylindrical axis. In the case of glasses and helmets, for example, the cylindrical axis is vertical and the plane is preferably horizontal. In this way, the light rays are incident on the input grating 132 at the same angle in this plane. A wavefront shaping device 135, for example a cylindrical lens and / or mirror, can be used for this task. As is usual in optical design best practices, the light rays of the central pixel are advantageously incident at an angle perpendicular to the surface of the waveguide 106 to facilitate aberration management for symmetry. Other pixels in this plane generate light rays that are incident on the input grating at other angles, but parallel to other light rays from the same pixel.

[0023] However, in a plane perpendicular to the cylindrical axis, e.g., the horizontal plane, the light may not be collimated, but rather shaped so that light rays from the same pixel have the same angle of incidence with respect to the surface normal, which is considered separately for different points of incidence. A wavefront shape that satisfies this condition is a cylindrical wavefront that is concentric with the cylindrical shape of the waveguide. The light rays from the central pixel then propagate radially from the cylindrical axis of the waveguide and approach the surface at normal incidence. This wavefront is advantageously formed by positioning the image source S (display) with its center at the waveguide axis. The cylindrical lens 135 or mirror is then positioned to have optical focusing power only in the vertical plane.

[0024] Optionally, additional or different input optics may be provided, for example, to optimize the performance of more or all pixels and / or to minimize the volume of the projector. This may include utilizing optics focused in the horizontal plane to bring the display closer. If a concave mirror is used, the image source and / or input coupling optics may be positioned such that light approaches the waveguide from the opposite side of the waveguide from the mirror before being reflected and then diffracted.

[0025] Light may propagate through the cylindrical waveguide 106 (e.g., between the input and output coupling optics) in a direction (defined by a vector) parallel to the cylindrical axis (e.g., vertical), or in a direction (defined by a vector) perpendicular to the cylindrical axis (which may be specifically horizontal around the circumference of the waveguide), or in a direction defined by a vector that is between vectors parallel and perpendicular to the cylindrical axis (typically a diagonal).

[0026] As illustrated in FIG. 4, the output coupling optics typically includes the output coupling grating 134 vas described above. In principle, a linear grating could be used. However, a practical application of the waveguide 106 is that the viewer is inside a cylinder. A simple linear grating may therefore not be appropriate to extract light in such a situation, since it would focus it in the horizontal plane of the cylinder axis (resulting in a vertical line of light) rather than far in front of the viewer. In contrast, a diverging lens property may collimate the light in the horizontal direction (which is already collimated in the vertical direction). This can be achieved by adding negative optical power to the output grating in the horizontal direction. By analogy, the grating is the sum of a prism function and a cylindrical negative lens function. There are many known examples of how to record such gratings. Such gratings are not referred to as "linear" in contrast to the input gratings. The output grating can be chosen to place the digital image at any distance from the viewer by adding more focusing power in both planes.

[0027] If the cylindrical waveguide 106 is embedded in a head mounted structure that is already compensated for the user's vision (e.g. prescription glasses), the input and output gratings may also be compensated to take this into account. The main factor is to preserve the aforementioned conditions of the light as it propagates within the waveguide, regardless of how it approaches and leaves the overall optical stack "sandwich."

[0028] A waveguide 106 of the type discussed above is placed between a first lens half 102 and a second lens half 104 to form a spectacle lens 100. FIG. 1a illustrates the final formed spectacle lens 100, and FIG. 1b illustrates an exploded view of the first and second lens halves 102, 104 with the waveguide 106 in between. The first lens half 102 has a spherical exterior front or outer, world-facing surface, and a cylindrical back surface, with a radius of curvature that matches and is matable with the radius of curvature R2 of the world-facing surface 108 of the waveguide 106. The second lens half 106 has a cylindrical exterior front or outer, world-facing surface, and a spherical back or outer world-facing surface, with a radius of curvature that matches and is matable with the radius of curvature R1 of the eye-facing surface 108 of the waveguide 106. It can be seen that the thickness t of the waveguide 106 around its circumference is equal or constant. Thus, those skilled in the art will understand that the waveguide 106 and the associated input coupler 132 and output coupler 134 are located between the first lens half 102 and the second lens half 104. With reference to FIG. 1c, a side view of the spectacle lens 100 illustrates the waveguide 106 interposed fitably between the first lens portion 102 and the second lens portion 104, and it can be seen that the thickness t of the waveguide 106 downward from the vertical edge of the waveguide 106 is equal or constant, thus the waveguide is flat in one axis. It can thus be seen that the cylindrical surface of the first lens portion 102 is concentric with the cylindrical surface of the second lens portion 104, and thus the remaining surface is spherical. The constant thickness of the waveguide around its perimeter and across its vertical edges ensures that light rays propagate uniformly through the waveguide. In this way, from an optical perspective, the waveguide 106 can be considered a flat lens, since it has zero optical power and does not contribute to the optical power of the eyeglass lens.

[0029] In each of Figures 1a-1c, (x-), (y-), and (z-) axes are shown for reference purposes, and these references are used throughout this specification. With reference to Figure 1a, an eyeglass lens 100 according to an embodiment has a major axis in the horizontal (x) direction, a minor axis in the vertical (y) direction, and a depth (z) direction. The depth (z) dimension of an eyeglass lens is typically significantly smaller than the dimensions in the (x) or (y) directions, by a factor of about 10.

[0030] Simple spherical lenses can be used as zero power lenses in applications such as off-the-shelf sunglasses and ski goggles. In such applications, the eye-facing and world-facing surfaces have spherical curvatures, where the world-facing surface curvature is known as the base curvature, and the two surface profile curvatures are non-concentric. The base curvature of the lens provides the best optical performance of the lens while achieving optimal aesthetics and reducing the weight of the lens. For example, a 6 diopter curved front (world-facing) lens surface, corresponding to a radius of curvature of approximately 83 mm, is considered the best form based on empirical data for providing the best peripheral vision for most users. For aesthetic reasons, reading glasses and fashion lenses can have a flatter surface with a typical base curve of 4 diopters, where the first lens portion 102 has a base curve of +4 diopters and the second lens portion has a base curve of -4 diopters (giving a net zero (0) diopters). Typically, the front, world-facing surface of the first lens portion 102 is curved to provide better vision and improve vision across the user's field of view, especially compared to a planar convex lens. Power may be added to the eye-facing surface of the second lens portion 104 to correct astigmatism. With respect to astigmatism, the second lens portion 104 may have a base curve selected to correct the astigmatism of the user's eye and to correct the astigmatism of the cylindrical waveguide 106, where the amount of astigmatism of the cylindrical waveguide 106 depends on the radii of curvature R1 and R2. Similarly, a net power may be added (or subtracted) by modifying the power of the second lens portion 106 to correct myopia or hyperopia.

[0031] As a non-limiting example, the spectacle lens 100 according to the embodiment may have a horizontal dimension (x-axis) of 55 mm, a vertical dimension (y-axis) of 32 mm, and a combined thickness (z-axis) of the first and second lens portions 102, 104 of 2 mm for a zero power stock lens. The eye-facing surface of the second lens portion 104 may have a radius of curvature of 150 mm (approximately 3.3 diopters). The world-facing surface of the first lens portion 102 may have a radius of curvature of 152 mm. The eye-facing surface of the first lens portion 102 and the world-facing surface of the second lens portion 104 are cylindrically curved in the xz plane, flat in the yz plane, and flat in the xy plane. The cylindrically curved surface of the first lens portion 102 has a radius of curvature of 125 mm in the x-axis, and the cylindrically curved surface of the second lens portion has a radius of curvature of 126 mm in the x-axis. The contour of the cylindrical surfaces of the first and second lens portions 102, 104 is flat in the y-axis. The difference in the radii of curvature accounts for the thickness of the cylindrical waveguide 106 and allows for conformal attachment of the concentric circular surfaces of the waveguide 106 to the cylindrical surfaces of the first and second lens portions 102, 104.

[0032] According to the present disclosure, the waveguide 106 may have a thickness t of 0.1 mm to 10 mm, preferably 0.5 mm to 2 mm, with radii of curvature R1 and R2 based on a lens curvature of 2 to 6 diopters, giving a radius of 80 to 300 mm. The first and second lens portions 102, 104 may typically be manufactured separately, but may optionally be formed by separating or splitting a single eyeglass lens. The cylindrical surface profile of the first and second lens portions 102, 104 may be created by grinding or injection molding, or a combination of the two. Optionally, 3D printing may be used to create the lens portions. The lens grinding and mold manufacturing process may use diamond grinding to achieve the cylindrical surface.

[0033] 1a, 1b, and 2, the eye-facing surface of the first lens portion 102 and the world-facing surface of the second lens portion 104 define a cylindrical interface into which the waveguide 106 matingly fits. As a non-limiting example of the above, the radii of curvature of the cylindrical surfaces of the first lens portion 102 and the second lens portion 104 may be 126 mm and 125 mm, respectively, defining a waveguide thickness of 1 mm. Because the waveguide is conformal with the cylindrical surfaces of the first and second lens portions 102, 104, the respective radii of curvature are the same as the corresponding surfaces of the waveguide 106. In other words, the eye-facing surface of the first lens portion 102 has a radius of curvature equal to R1, and the world-facing surface of the second lens portion 104 has a radius of curvature equal to R2. The first lens portion 102 is thicker in the central section than in the outer sections, while for a positive user prescription, the outer section of the second lens portion is thicker than the central section, or for a negative user prescription, the outer section of the second lens portion is thinner than the central section.

[0034] While the above discussion relates to purely cylindrical surfaces of the first and second lens portions 102, 104 and the surface of the waveguide 106, those skilled in the art will understand that those surfaces may be partially spherocylindrical or toric, provided that any deviation from a purely cylindrical shape is negligible and provided that the thickness of the waveguide 106 remains constant.

[0035] The waveguide 106 may be attached to the first and second lens portions 102, 104 by any suitable means. For example, the waveguide 106 may be attached by a transparent adhesive applied to each of the cylindrical surfaces of the first and second lens portions 102, 104, or the waveguide 106, or both. The transparent adhesive may be a low index material, such as Norland Optical Adhesive 1315, for example, which has a refractive index of 1.315. This has the advantage that the adhesive serves to mechanically secure both the first lens portion 102 and the second lens portion 104 to the waveguide 106, but also maintains the necessary refractive index difference to allow total internal reflection within the waveguide. As an example, the transparent adhesive has a thickness of 20 μm to 100 μm. The adhesive may be an adhesive film or tape, or a liquid adhesive. Furthermore, the adhesive may be viewed as a transparent medium that serves as a cladding material for the waveguide 106, necessary to achieve the refractive index difference mentioned above. For example, if the adhesive is 0.1 μm thick and applied to both of the concentric cylindrical surfaces of the waveguide 106, appropriate adjustments can be made to the radii of the cylindrical surfaces of the first and second lens portions 102, 104 to account for the additional thickness of the transparent adhesive material. It should be noted that from an optical standpoint, the thickness of the transparent adhesive material does not need to be uniform across the cylindrical surface of the waveguide 106, and any variations will not affect the total internal reflection of the waveguide 106 if the thickness is non-zero. In terms of the refractive index difference required to achieve total internal reflection within the waveguide 106, a typical exemplary difference between the waveguide and the transparent adhesive may be 0.5. Taking the exemplary refractive index of the transparent adhesive as 1.3 (as shown above), the waveguide should have a refractive index of 1.8 and may be formed, for example, from lanthanum glass, resulting in a 40 degree field of view (FOV) total internal reflection. It is possible to change the field of view of the waveguide by appropriate selection of the refractive index of the waveguide, where a higher refractive index waveguide material allows for a higher field of view.

[0036] Alternatively, the waveguide can be made of BK7 glass, which has a typical refractive index of 1.52; in this example, to achieve a refractive index difference of 0.5, the transparent adhesive should have a refractive index difference of 1.02. SF11 glass, with a refractive index of 1.78, can also be used as a waveguide material. Schott AG also offers waveguide materials with refractive indices up to 2.0; to achieve a refractive index difference of 0.5, the transparent adhesive should have a refractive index of 1.5.

[0037] Alternatively, keeping in mind the requirement of refractive index difference, there may be an air gap at the interface between the cylindrical surfaces of the first and second lens portions 102, 104 and the waveguide 106. Those skilled in the art will appreciate that the refractive index of air is 1.0, whereas, as mentioned above, the refractive index of the waveguide 106 should be 1.5. Thus, the air gap may be considered as the cladding material required to achieve the required refractive index difference. In this case, a small amount of adhesive is required around the lens portions to mechanically secure the first and second lens portions 102, 104 to the waveguide 106. This small amount of adhesive material also serves to environmentally seal the air gap from the ingress of contaminants such as moisture. As an alternative to adhesive, the air gap may be sealed and the respective portions of the waveguide 106 may be secured and heat sealed to the respective portions of the first and second lens portions 102, 104. In the case of an air gap anti-reflective coating, it may be applied to the spherical surfaces of the lens portions and / or the waveguide to prevent back reflections and ghost images. In the case of an air gap, the first and second lens portions 102, 104 should ideally be formed of a relatively stiff material, such as glass, rather than polycarbonate, which is relatively flexible. This reduces the chance that any bends in the lenses will cause them to touch the waveguide and result in light leakage from the waveguide 106.

[0038] Alternatively, the first and second lens portions 102, 104 may be formed from a low index material and the waveguide 106 may be formed from a high index material, and in this way the first and second lens portions 102, 104 may be seen as the cladding material of the waveguide required to achieve the index difference. In this case, spectacle lenses usually require high index materials to reduce weight. Plastic lenses typically have an index of refraction between 1.3 and 1.8. Typically, polycarbonate lenses are between 1.5 and 1.6, while Trivex (RTM) material is 1.53 or CR39 (RTM) is 1.49. High index plastics are available with an index of refraction of 1.8. Thus, following the above discussion, one skilled in the art would understand that to achieve the index range of 1.3 to 1.8, a waveguide material with an index of refraction between 1.8 and 2.3 is required. Schott AG 2.0 index waveguide material in conjunction with Trivex (RTM) or CR39 material will provide the required 0.5 minimum index difference. As a further alternative, the waveguide 106 may include a transparent cladding material, thereby providing the necessary index difference for total internal refraction. As yet another alternative to adhesives, the first and second lens portions 102, 104 and the waveguide may be heat sealed directly to the waveguide, provided that the index difference can be maintained using one of the options discussed above.

[0039] With reference to the above discussion regarding the radius of curvature of the waveguides R1 and R2, in practice, when an adhesive material is used to attach the first and second lens portions 102, 104 to the waveguides, or when an air gap is utilized, one skilled in the art will appreciate that the radius of curvature of the waveguides R1 and R2 will not exactly match the radius of curvature of the cylindrical surfaces of the first and second lens portions 102, 104 due to the thickness of the adhesive or air gap. However, the thickness of the adhesive or air gap can be neglected.

[0040] FIG. 3 is a schematic diagram of a cylindrical waveguide 106 illustrating the optical properties, with the lens portion omitted for clarity, as in FIG. 2. In addition to the waveguide 106, an input coupler 132 is also illustrated. A collimated ray can be coupled into the waveguide 106 by the input coupler 132 at an angle β (in-coupled). The ray incident on the input coupler 132 is normal to the surface at all points on the surface of the input coupler 132, and the angle β is such that the angle between the normal and the internal ray in the waveguide 106 is less than the critical angle of the waveguide 106. For example, the angle β is typically less than 48 degrees. More preferably, the angle β is at least 30 degrees and at most 40 degrees. Rays other than the central ray are coupled into the waveguide 106 at a slightly different angle, e.g. β+1, but this angle is consistent at all points along the surface of the input coupler 132. The input coupler 132 may be a diffraction grating or a holographic grating.

[0041] Those skilled in the art will appreciate that the light beam may originate from an image source S located at the center of a radius of curvature X of a concentric circular surface of the waveguide 106. The light beam from the central pixel of the image source S may be collimated in one plane by a collimating lens 135. This collimation of the light beam is a form of wavefront shaping for coupling the collimated light beam into the waveguide, as described above.

[0042] If the opposing surfaces 108, 110 of the waveguide 106 are concentric as illustrated in Figures 2 and 3, the angle of incidence of the light ray on the outer surface 108 will be the same after reflection on the opposing inner surface 110, and therefore the light ray will retain its direction angle as it propagates through the waveguide 106, which is not the case for curved waveguide configurations that do not have concentric circular surfaces. As illustrated in Figure 3, if the angle of incidence with the world-facing surface 108 is α, the angle of incidence with the eye-facing surface 110 will be β, and the subsequent angle of reflection from the world-facing surface 108 will be α. In other words, the angle of incidence within the waveguide is the same for all alternate reflections from each surface of the waveguide 106. Light rays from pixels entering the left, center, or right of the input coupler 132 approach the inner surface at the same angle throughout the entire waveguide after reflection from the world-facing surface 108. Pixels other than the central pixel will have different values ​​of α and β, but the relationship between incidence and reflection above will still be valid.

[0043] It has been recognized that a high performance, compact optical system can be implemented by making all light rays originating from the same point on the image surface enter the cylindrical waveguide 106 at the same angle. 2 ), the output brightness at the output (from the user's perspective) is in the region of 10,000 nits, which corresponds to a system efficiency of 10%, where losses can be mainly attributed to losses in the input coupling gratings 132, 134.

[0044] While the central ray angle is discussed in this disclosure, there may be other ray angles generated by an image source S, such as a microdisplay or a laser beam scanning projector, which may be magnified and collimated for use in the waveguide to generate a field of view of an image viewed by a user during use. These other ray angles propagate through the waveguide 106 in the same manner as the central ray, except that at the edges of the field of view, or the edges of the image, there will be some loss of image quality or aberration of the rays, but if kept below one arc minute, the limit of human vision, such aberrations will be largely unnoticeable to the user. In any case, the aberrations can be compensated for by optical means such as multiple element, large, high quality, aspheric, long focal length collimating optics to reduce the aberrations at the edges of the field. Advantageously, the aberrations do not accumulate with the number of internal reflections within the waveguide 106. For example, if a ray from a given pixel is in-coupled into the waveguide 106 at an angle of 60±0.1 degrees, then after any number of reflections and pupil duplications, regardless of how the ray is swapped or shuffled, the angular resolution of the waveguide 106 and in-coupling optics will still support a resolution of ±0.1 degrees. This is in contrast to a waveguide accumulating aberrations along its transmission length.

[0045] FIG. 4 illustrates a schematic top-down view of a waveguide as illustrated in FIG. 2 and FIG. 3, except that an output coupler 134 is included. The output coupler 134 can be a diffraction grating or a holographic grating applied to the surface of the waveguide 106, and the output coupler 134 is preferably coincident with the input coupler 132. That is, the central guided angles of the waveguide for the input coupler and the output coupler (in other words, the TIR angles for the central pixel, central ray) are the same and at the same wavelength. For reference only, in FIG. 4, the plane of the page (and any plane parallel to it) is considered to be a horizontal plane. Similarly, the vertical plane outside the page (and any plane parallel to it) is considered to be a vertical plane. In this way, the cylindrical waveguide can be considered as a cylindrical visor on a flat table, etc. As previously discussed, the image source S may be located at the center of the radius of curvature of the concentric circular surface of the waveguide 106 and may be collimated in one plane (in this example, the vertical plane) by the collimating lens 135. The light rays entering the waveguide 106 from the input coupler 132 propagate along the waveguide, which has rotational symmetry, as described above. In other words, the waveguide as illustrated in FIG. 4 can be rotated about a cylindrical axis, and the light rays from a given pixel will maintain the same angle with respect to the cylindrical surface of the waveguide. This rotational symmetry makes the waveguide invariant to the position of the placement of the output coupler 134 on the waveguide 106, thus eliminating the need for precise alignment of the output coupler 134 on the waveguide 106. Thus, light collimated in one plane by collimating lens 135 enters waveguide 106 at input coupler 132, propagates through waveguide 106, and then exits waveguide 106 at output coupler 134 to provide light to the user's eye.

[0046] The waveguide 106 allows the spherical wavefront from the source S to conform to the curvature of the waveguide 106 by itself in the horizontal plane, and power is added in the vertical plane by the cylindrical lens 135. This means that after two reflections of the ray in the waveguide 106, the ray is mapped back onto itself, and this is repeated indefinitely. Thus, the pupil can be replicated and expanded to expand the eyebox in one dimension (horizontally in this case). The collimating lens 135 may be integrated into the augmented reality glasses lens system, as discussed below, or may be provided externally, such as in a display projector system. The size of the vertical eyebox is set by the vertical size of the cylindrical lens 135. Also, alignment tolerances are relaxed (since the position of the output coupler relative to the input pupil is not critical for the thickness of the waveguide and the choice of the central ray guide angle). If vertical replication is required, a so-called "rotating grating" for vertically expanding the eyebox may be used.

[0047] Referring to FIG. 5, a perspective view of the curved waveguide 106 of the eyeglass lens 100 according to an embodiment is illustrated. Again, the first and second lens parts are omitted for clarity. Light rays from an image source S, which in this case may be a microdisplay, are collimated in one plane by a collimating lens 135 and coupled into the waveguide 106 by an input coupler 132. The light rays propagate through the waveguide 106 and are coupled into the user's eye by an output coupler 134. The image source S is at a distance from the waveguide 106 that is the same as the radius of curvature of the waveguide to which the input coupler 132 is applied (R1 in this example), which is achieved by physically placing the image source S at this distance or virtually placing the image source at this distance by optical means, for example using a lens. The image is collimated in one plane by a collimating lens 135, which may be a cylindrical planar convex lens, onto the input coupler 132 located on the concave inner surface of the waveguide 106. The collimating lens 135 is oriented such that the focusing power of the collimating lens is in an opposing plane compared to the waveguide 106. When the waveguide 106 is oriented horizontally (as illustrated), it has power in the vertical plane and reflects light from a point source at a radius of curvature into a vertical line. The collimating lens 135 is then oriented in the opposing vertical plane and has power in the vertical plane to focus light from a point source at a radius of curvature into a horizontal line. Thus, the light rays carrying the image information are collimated in only one plane (horizontal) before entering the waveguide 106, and the curvature of the waveguide 106 matches the light in the vertical (vertical) plane. This allows the entire pupil of light entering the waveguide to propagate along the waveguide 106, thus allowing pupil expansion from the output coupler 134 at the output to the user's eye.

[0048] The focal length of the collimating lens 135 determines the object magnification, and the lens 135 is set at a distance of one focal length from the source S. If the cylindrical lens 135 is placed next to the cylindrical waveguide 106, it will have a focal length approximately equal to the radius of curvature of the waveguide. For example, a typical radius of curvature of a visor-shaped waveguide is 200 mm, meaning that the object is 200 mm away and the focal length of the cylindrical lens is 200 mm. The 200 mm distance from the waveguide to the object can be shortened for compactness by folding the optical path with a mirror or optically setting the object distance virtually using a lens.

[0049] The choice of collimating lens 135 (diameter and / or focal length) determines the size of the vertical eyebox (determined by the diameter of the lens), and the focal length determines the magnification of the light source S and therefore the field of view (FOV) of the image (along with the size of the display). Typically, a multi-element lens is used to collimate lens 135 (as used in a camera), which provides good image quality (small spot size RMS across the entire field) across the entire FOV. This is particularly desirable for a pupil replication system to accurately overlay the pupil and provide a high resolution image. The lens system is ideally achromatic for full color microdisplays, although monochrome solutions are possible. The FOV of a curved waveguide 106 may be determined primarily by similar factors, but due to the nature of the curve around the user, the FOV is expanded compared to a planar waveguide.

[0050] The input coupler 132 is a linear grating and may be a diffraction grating with equal surface spacing (pitch) between the grating lines (or equivalently, equal fringe spacing in a volume holographic grating). The grating can be fabricated lithographically or interferometrically. Typically, all rays collimated in one plane incident across the width of the grating surface (90 degrees to the surface) are then diffracted at the same angle in the waveguide, which allows pupil duplication.

[0051] A grating on a curved waveguide typically means that the collimated light does not normally enter over the grating width due to the curvature of the waveguide. Typical solutions to this involve varying the pitch of the grating to compensate for this, or recording a hologram directly on the curved surface, or lithographically etching the curved surface, which is complicated and expensive. In a preferred embodiment according to the present disclosure, the input coupler grating 132 is fabricated as a planar linear grating on a flat substrate (well known to those skilled in the art and relatively cheap and easy to manufacture compared to tunable gratings). The input coupler grating 132 can be made on any flexible holographic material, for example a photopolymer (e.g. Bayfol (RTM) or silver halide film, commercially available by Covestro AG), and is then attached (laminated) onto the cylindrical surface of the waveguide so that it conforms to the cylindrical surface. The input coupler grating 132 is preferably index matched by lamination (or another index matching adhesive or liquid) so that it conforms to the shape of the cylindrical surface and is preferably free of air gaps. It is easy and cheap to record a hologram on a flat substrate and then remove and laminate flexible holographic material onto a planar or cylindrical substrate (curved in only one dimension), whereas recording on a curved surface or laminating on a spherical surface (curved in two dimensions) is more difficult. It may also be possible to etch a tilted grating and use embossing or UV-cured resin techniques. The grating may then be transferred to a cylindrical waveguide.

[0052] The pitch of the input coupler grating 132 is designed to diffract the central wavelength of the source S. Because the input coupler grating 132 is nominally designed to diffract normally incident light at an angle, the input coupler grating 132 has a tilt angle and the pitch is usually specified as the separation between the gratings as measured along the planar surface of the grating. This keeps the input coupler grating 132 constant, i.e., a linear grating.

[0053] In the case of known planar waveguides, both couplers are typically linear and identical. The system then operates like a periscope, and a magnified image of the microdisplay overlaid on the real world is presented to the viewer. The design of the entire system means that the position pixel information of the display is converted through collimation into angular information and then back into position information at the human retina. Similar to the input coupler 132, the output coupler 134 can also be a diffraction grating with a variable period along the waveguide, which does not cancel chromatic aberrations everywhere if the light source S is a broadband source. However, the period of the central grating can be chosen to be identical to the input grating period in order to minimize such aberrations.

[0054] Alternatively, narrowband sources such as laser sources, superluminescent light emitting diodes (SLEDs), or notch filtered narrowband LEDs can be used. Narrowband sources can help minimize chromatic aberrations. They can also limit the FOV of the output image, but thin holographic volume gratings can be used to mitigate this. For example, a typical thickness of a holographic volume grating can be at least 3 microns and up to 6 microns. The thickness of the holographic volume grating can be selected depending on the required diffraction efficiency (DE) and FOV. Increasing the thickness provides a higher DE but a lower FOV. This can provide a typical spectral bandwidth of about 20 nm full width at half maximum (FWHM) and an angular bandwidth in air of about 6 degrees FWHM.

[0055] The output coupler grating can be selected to place the digital image at any distance from the viewer by adding more foci in both planes. In the vertical plane, the light in-coupled into the waveguide is collimated, but the light output from the output coupler grating does not need to be collimated. To allow for multiple pupil extraction, only a portion of the light may be extracted in a first portion of the output coupler grating 134. To balance the uniformity of the light extracted across the output coupler grating 134, it is desirable for the far end of the output coupler grating 134 (relative to the input coupler grating 132) to have a higher efficiency than the near end (receiving end). The diffraction efficiency (DE) of the output grating is advantageously selected low enough to allow sufficient pupil duplication (e.g., 5-25%) at the receiving end of the output grating 134, but high enough for satisfactory brightness (e.g., 10-100%) at the far end.

[0056] Referring to FIG. 6, a schematic top-down view of the cylindrical waveguide 106 and a simplification of the output coupling optics including the output coupler 134, which may be a diffraction grating, is shown. As with FIG. 4, the plane of the page (and any parallel planes) of this drawing is considered horizontal, and the vertical plane (and any parallel planes) coming out of the page is considered vertical. Thus, the cylindrical waveguide 106 can be visualized, for example, as a cylindrical visor on a flat surface. In this simplification, a cylindrical negative lens 155 is also shown, as will be discussed further below. As indicated by line 152, the light beam 151 output from the output coupling grating 134 is collimated in the vertical plane and focused in the horizontal plane. The light beam 156 output from the cylindrical negative lens 155 is collimated in both the x-horizontal and y-vertical planes and has a focus at infinity. This is a simplification because the cylindrical negative lens 155 is actually optically integrated within the output coupling grating 134. Thus, power is included in the output coupling grating to compensate and achieve collimation in both planes at the output, whereby the output coupling grating 134 acts as a cylindrical lens to compensate for the cylindrical curvature introduced by the input coupling optics, thus essentially collimating the image at infinity, as described below.

[0057] Due to the asymmetric collimation in the input coupling optics, the output coupling optics compensates for the different focal positions of the horizontal (near) and vertical (far or infinity) output image planes to provide images focused to infinity in both planes, thereby providing a high quality image to the viewer. The compensation is achieved by encoding the optical power into the output grating. As shown in FIG. 6, it is equivalent to placing a diverging cylindrical lens 155 with a negative power equal to the radius of curvature of the waveguide between the planar output grating and the user (for a planar concave cylindrical lens, if the radius of curvature of the waveguide is 200 mm, the focal length of the lens is 200 mm). The lens 155 is oriented perpendicular to the input collimating lens 135. If the collimating lens 135 is focused (or has power) in the vertical plane, the output compensation lens / grating will be focused (or has power) in the horizontal plane, producing a spherically collimated output. As discussed above, the center of the output coupling grating 134 has the same surface pitch (also known as lateral pitch or in-plane pitch) as the input grating to enable chromatic dispersion compensation.

[0058] The image is presented to the user at infinity. This is typically the desired use case since it means that the virtual image appears in focus when the user is focusing on a distant object in the real world, as is typical when using a visor, such as a fighter pilot or motorcycle rider. Consumer devices using planar waveguides with pupil expansion also have images at infinity. Alternatively, rather than setting the image at infinity as discussed, it is possible to bring the virtual image closer to the user by adding negative power in the output coupler. For example, 1 diopter of negative power in a holographic output coupler sets the image at 1 meter rather than infinity, which may be useful if the user wishes to overlay the virtual image at a focal plane equal to, for example, arm's length.

[0059] The output grating 134 can have a varying grating efficiency, or a relatively low output efficiency (e.g., 10%). This can be achieved during recording of the holographic output coupler. While it is desirable for the input grating 132 to have maximum diffraction efficiency (meaning that most of the light incident on it is coupled into the waveguide), the output grating 134 can have a lower or variable efficiency that allows for pupil expansion. A small portion of the light is coupled out on a first interaction with the output grating 134, while a larger portion bounces back down the waveguide and some of that light is output on a second interaction, and so on. This allows for an expanded eyebox in the horizontal plane.

[0060] Holographic waveguide gratings (either linear or degreed output couplers) can be fabricated by exposing a holographic material to two coherent light beams, with the waveguide beams coupled into the material through a prism, as known in the art. Using lasers of three different wavelengths (e.g., red, green, and blue, RGB), three gratings can be multiplexed into a single holographic layer, allowing the viewer to see a substantially white image from an RGB microdisplay. Alternatively, three separate layers can be stacked, one for each color.

[0061] The FOV provided to the user, who sees a uniformly bright and chromatically uniform image throughout, can be increased by multiplexing multiple gratings onto a single holographic layer. This can be achieved by varying the recording angle. Alternatively, multiple angle-multiplexed layers can be stacked.

[0062] The input and output gratings can be reflection holograms, transmission holograms, or any combination thereof. This will be understood from the theory above, since the desired effect is based only on the lateral component of the grating pitch. The transverse (cross-sectional) pitch or period can be conveniently selected to match the reflection or transmission grating geometry. Linear gratings above mean linear in the lateral direction, but it can also be understood that they can have variable lateral properties.

[0063] The collimated nature of the output light means that a large eye relief (i.e. the distance at which the eye can be behind the output surface and optimally view the image) can be achieved. This is often desirable, especially in applications where a helmet visor is used rather than glasses. A larger eye relief typically results in a smaller FOV.

[0064] The view of the real world will be barely altered by the curvature of the waveguide. A radius of curvature of 250mm for glasses and 150-200mm for visors is normal. Any curvature greater than 100mm (as is the case here) will not be noticed by the user as a real-world distorting effect. Only very small astigmatism effects will be present unless compensated for by an additional overlay lens (or multiple overlay lenses).

[0065] Returning to the generalized meaning of this disclosure, the output coupling optics may be considered to include an output coupling grating. In particular, the output coupling grating may be configured to function as a cylindrical lens (e.g., to focus in only one dimension). Additionally or alternatively, the output coupling linear grating may have a curved grating. In a preferred embodiment, the output coupling linear grating may have an internal grating angle arranged to collimate the received light in a plane, or to focus the received light in the tangential and sagittal planes at a predetermined distance, and / or to focus the output efficiency or diffraction efficiency at the end of the output coupling grating nearest the light received from the input optics of 25% or less (optionally 20%, 15%, or 10%).

[0066] The output coupling optics may include an output wavefront shaping device configured to collimate the received light in a single plane orthogonal to the single plane of the input wavefront shaping device. Additionally or alternatively, the output coupling optics may include a cylindrical negative lens. Preferably, such an aspect is integrated into the output coupling grating.

[0067] The out-coupling linear grating may have the same surface pitch as the in-coupling linear grating. In some embodiments, the out-coupling linear grating may have an internal grating angle oriented in the opposite direction compared to the internal grating angle of the in-coupling linear grating. This is particularly used when the light from the image source and the light to the viewer (or the in-coupling optics and the out-coupling optics) are on the same side of each other. This may be referred to as a "U" grating. Alternatively, the angles of the in-coupling grating and the out-coupling grating are not oriented in the opposite direction, and at least some light is out-coupled on the opposite side of the in-coupled light (in other words, the viewer is on the opposite side compared to the in-coupling light). This may be referred to as a "Z" grating.

[0068] From an alternative perspective, the approaches according to the present disclosure can also be described in terms of symmetry: they use cylindrical waveguides and cylindrically symmetric wavefronts, both of which are rotationally symmetric about a common axis.

[0069] Consider a pixel on a display or other image generating means. It is possible to shape the light wavefront from this pixel into a cylindrical shape. A linear diffraction grating recorded on a flat substrate and laminated onto a cylindrical waveguide has a constant period along the surface. Then all the light rays are deflected by the same angle, making the light field symmetric around the axis of rotation. As explained above, a light ray launched between cylindrical surfaces will retain its two angles of incidence on the two surfaces no matter how many times it bounces. This means that after every two reflections, the wave will exactly coincide with itself. This does not produce a double image. Such a light field can propagate any distance without any ray becoming different from the other.

[0070] Also, pupil duplication at the output grating is achieved: partial out-coupling of light occurs at the first interaction with the out-coupling optics, while the remaining light propagates and couples out at the next interaction. In this case, the different interactions coincide perfectly without causing ghost images. When all the rays reach the out-coupling grating, the grating can diffract them out of the waveguide, regardless of the position of the grating or the position of any one ray, since they all arrive the same.

[0071] Using a linear output coupling grating with the same period as the input coupling grating, the light rays are diffracted again into a new cylindrical wavefront. It is well known that diffractive optical elements can combine several functions additively. The output coupling grating also has one-dimensional focusing power, like a cylindrical lens. This transforms the diffracted light into collimated light. An observer receiving such light experiences a star-like point at infinity.

[0072] The above description can be repeated for other pixels. As mentioned above, the wavefronts from these other pixels do not need to be exactly cylindrical. This occurs because the rays from the non-central pixels enter the input coupling optics at angles slightly different from the "perfect" right angle (perpendicular). However, by hitting all input couplers at substantially the same angle relative to the surface normal at their respective intersection points, the resulting rays form a field of rays that is rotationally symmetric about the cylindrical axis and propagate in an indistinguishable manner. Using modern optical design, it is possible to design projectors that form such light fields with small errors, ideally within one arc minute (human visual acuity).

[0073] If the eye-facing surface of the second lens portion 104 is concave and there is an air gap or transparent adhesive between the waveguide 106 and the second lens portion 106, the second lens portion will add a converging force to the light coming out of the output coupler, so more negative (diverging) power needs to be added to compensate for this. That is, the output coupler needs to have more negative power (it may already have some negative power, as discussed above). If an amount of negative power equal to the inner surface radius of curvature is added, the virtual image remains at infinity. For the second lens portion 104, the world-facing surface may be cylindrical. Similarly, if the eye-facing surface of the second lens portion 104 is spherical, spherical negative power may be added to the output coupling grating, as well as cylindrical power. Note that the input coupler may be a transmissive or reflective geometry, but the reflective type is usually used for practical reasons. In the figure, the input coupler appears to function as a transmission hologram that is in fact a reflection hologram; what happens is that light passes through the hologram, bounces off the outer hologram surface, and is then diffracted in the reflection geometry (for the output coupler).

[0074] The orientation of the cylindrical waveguide can be varied. The above-described embodiments relate to the cylindrical axis of the cylindrical waveguide being vertically oriented (so that the cylindrical waveguide extends horizontally) since this is the usual way to align the visor. Other orientations can be considered. Additionally or alternatively, light may enter and exit the cylindrical waveguide through different surfaces, for example on different sides of the waveguide. To achieve this, the input and output coupling gratings can be positioned accordingly. In some embodiments, multiple input and / or output coupling gratings can be provided.

[0075] The input and output coupling gratings may each be reflective or transmissive gratings and may be located on the inner or outer surface of the waveguide (or on another surface of the waveguide). Those skilled in the art will appreciate such variations on the embodiments shown herein.

[0076] Furthermore, it is known that the human eye seems to prefer viewing in a horizontal aspect ratio (for example, the aspect ratio of televisions is optimized for this), eyeglass lenses are mostly horizontal aspect ratios, and the aspect ratio of the output coupler matches the aspect ratio of the lenses. Also, the fact that the IPD varies more horizontally than vertically means that a large horizontal eyebox, rather than a vertical eyebox, is advantageous to the user.

[0077] The input pupil is twice the width of one bounce so edge rays do not overlap the input coupler grating. The optimum pupil width is set by the waveguide thickness and steering angle, and is approximately twice the thickness of the waveguide. So a very thin waveguide means a very small pupil (0.5mm thick = 1mm pupil), so to get a large eyebox you need to overlap many pupils with the output coupler grating.

[0078] The linear input grating can have any angle of orientation. The light does not have to be redirected in the cylindrical circumferential direction (perpendicular to the cylindrical axis, which is horizontal in the above embodiment). It can be directed along the cylindrical axis (vertical). Alternatively, it can be directed at 45 degrees or any other diagonal direction. This allows more design freedom, such as conveniently placing the projection module on the temples of glasses (eyeglasses). This is also important for the realization of intermediate gratings for 2D pupil expansion. The intermediate linear grating can redirect and / or separate light while keeping the respective angle of each redirected ray the same for rays from the same pixel.

[0079] The system allows for the use of either laser or LED light, which allows for flexibility. Typically LED light is used, e.g. LCOS (liquid crystal on silicon) plus LED or microLED microdisplays, but laser light can also be used if high efficiency and therefore brightness is desired. Laser beam mirror scanning systems (MEMS), micro-opto-electro-mechanical systems, can also be used. Laser light has some disadvantages in terms of cost, speckle (loss of resolution), and eye safety concerns.

[0080] When refractive elements (e.g., prisms) are used as input or output couplers in conjunction with diffractive input or output couplers, uncompensated chromatic dispersion may allow only narrowband sources (e.g., lasers) to be used. Additionally, refractive couplers tend to be bulky and expensive.

[0081] By adding spherical optical power to the waveguide output, it is possible to set the virtual image at a different focal length. It is also possible to use an additional lens pair (a second lens to compensate for the effect of the first lens in the real world) before and after the waveguide to bring the focal length closer. A further possibility is to add an electrically addressable switchable (liquid crystal based) holographic output grating that can be switched on or off to provide different focal planes for the image. Additionally or alternatively, the input grating can be switched in the same manner to provide a larger FOV, as can be achieved with an angle multiplexed grating. The switching can be synchronized with a time multiplexed microdisplay.

[0082] Optionally, multiple focal planes may be realized by using multiple (stacked) cylindrical waveguides. The light propagates as discussed above, but exits with a grating that creates different focal points. Furthermore, like a normal spherical lens, adding axially symmetric power to the output of a cylindrical waveguide will experience a point at a finite distance, e.g. 1 m.

[0083] The cylindrical waveguide may form part of a larger (integral) waveguide structure, only part of which may be cylindrical. An embodiment may be envisaged where no input coupling optics are required. For example, light may enter or originate from the waveguide in a part of the waveguide that is not cylindrical (e.g. due to an embedded image source) and wavefront shaping may be performed in this part. This part of the waveguide may therefore form part of the input optics.

[0084] The vertical eyebox can also be expanded by multiple vertically displaced input projectors. A typical approach used to expand the vertical eyebox of a planar waveguide uses a "turn" grating that propagates the pupil vertically to give a 2D exit pupil expansion. There are various methods to expand the eyebox vertically, including input and output gratings, as implemented in products from Vuzix Corporation or DigiLens Inc. An alternative is to use a "butterfly" turn grating, which expands the eyebox and also expands the FOV by splitting the FOV in two at the input and recombining it at the output (as used by HoloLens (RTM) sold by Microsoft Corporation). A further option is to use a cross-multiplexed grating, which guides some of the light and out-couples some of the light across the expanded eyebox (as used in products from WaveOptics, Ltd).

[0085] All of these existing techniques would benefit from the use of collimated light routed by linear gratings and planar waveguides. According to the present disclosure using cylindrical waveguides, these techniques of splitting the light and replicating the pupil with an intermediate linear grating can be implemented after in-coupling the light into a cylindrical waveguide. The light can then finally be out-coupled with a grating that has a negative cylindrical focusing function.

[0086] The rotationally symmetric structure of the embodiments according to the present disclosure allows the input and output gratings to be placed anywhere on the concentric cylindrical waveguide. For example, the orientation can be vertical or at an angle across the waveguide (e.g., in a visor implementation), similar to the typical planar horizontal configuration discussed above. This allows flexibility in projector placement and eyebox placement in the final design. It also allows for pupil duplication and vertical eyebox expansion methods discussed in the previous paragraph.

[0087] In an embodiment, the wavefront shaping device may include a concave (cylindrical) mirror. Optionally, the image source and / or image source mounting may be located closer to the outer surface of the cylindrical waveguide than to the inner surface of the cylindrical waveguide. The mirror (preferably the wavefront shaping device) may then be positioned to receive light from the image source and reflect the received light towards the cylindrical waveguide. In some embodiments, the mirror and the image source and / or image source mounting are configured such that the light from the image source passes through the cylindrical waveguide before reaching the mirror. In certain embodiments, the respective portions of the input optics (e.g., input coupling grating) proximate to the cylindrical waveguide and the output coupling optics (e.g., output coupling grating) proximate to the cylindrical waveguide are on opposite sides of the cylindrical waveguide.

[0088] In certain embodiments, the input optics further comprises one or more spherical lenses. Additionally or alternatively, the output coupling optics further comprises one or more spherical lenses. The spherical lenses may be used to change the optical path length of the light and / or to change the focus of the light.

[0089] In embodiments, the input optics may further include a waveguide portion integral with the cylindrical waveguide. Advantageously, the waveguide portion forming at least a portion of the input optics is non-cylindrical and / or does not have concentric circular surfaces. In some embodiments, only a portion of the shape of the waveguide may be cylindrical.

[0090] In some embodiments, one or more intermediate optical gratings may be provided in the cylindrical waveguide. One, some, or all of the one or more intermediate optical gratings may be linear. The intermediate optical grating or gratings may be arranged to redirect, diffract, and / or split the light before the output coupling optics. However, the relative angles of the light rays from the same pixel advantageously remain the same. The intermediate optical linear grating advantageously preserves the angular characteristics of the propagating light (TIR condition, and that all light rays from the same pixel are incident on the cylindrical waveguide surface at the same angle relative to the surface perpendicular to the cylindrical axis and at the same angle relative to the plane perpendicular to the cylindrical axis), thereby enabling aberration-free two-dimensional pupil expansion.

[0091] The output coupling optics may include an output coupling grating having one or more of an internal grating angle arranged to refract the received light, a variable diffraction efficiency along the length of the output coupling grating, and a switchable grating configuration (e.g., allowing for modulation of the output light). Optionally, the input coupling grating may have a switchable grating configuration.

[0092] An alternative arrangement of the eyeglass lenses discussed above is illustrated in Figures 7a-7c, with the difference being that the waveguide 106 extends outside the area of ​​the first and second lens portions 102 and 104 as an input coupling tab 161. The input coupler 132 may be formed or fixed on the input coupling tab 161, typically the input coupling tab being formed on the side of the AR eyeglass frame that contains the input light source. Additionally, input coupling optics such as a collimating lens 135 may be disposed on the input coupling tab 161.

[0093] A plurality of cylindrical waveguides may be provided. For example, a second cylindrical waveguide having concentric inner and outer surfaces may be provided. The first and second (or plurality) cylindrical waveguides may be stacked. Some or all of the plurality of cylindrical waveguides may have a common cylindrical axis. In all such cases, the input optics may be arranged to cause some of the received light to enter each of the plurality of cylindrical waveguides such that, for each cylindrical waveguide, all light rays originating from the same pixel of the image source are incident on the surface of the respective cylindrical waveguide at the same angle relative to a surface perpendicular to the respective cylindrical axis and at the same angle relative to a plane perpendicular to the respective cylindrical axis at each point of incidence, whereby the in-coupled light retains its directional angle as it propagates along the respective cylindrical waveguide. Beneficially, the output coupling optics may be arranged to focus the light propagated along each of the cylindrical waveguides at different focal points. For example, the output coupling optics may be arranged to focus light propagating along a first cylindrical waveguide at a first focal point and to focus light propagating along a second cylindrical waveguide at a second, different focal point.Embodiments may advantageously consider multiple image sources that are vertically displaced from one another.

Claims

1. 1. A spectacle lens for an augmented reality display, comprising: a first lens portion and a second lens portion, a cylindrical waveguide therebetween, and input optics for coupling light into the cylindrical waveguide; the cylindrical waveguide has cylindrical concentric opposing surfaces for propagating light along a waveguide having rotational symmetry, the cylindrical concentric opposing surfaces defining a first cylindrical interface with the first lens portion and a second cylindrical interface with the second lens portion, the cylindrical waveguide being transparent and including a central waveguide core having a transparent medium at the first and second cylindrical interfaces, the central waveguide core having a higher refractive index than the transparent medium, the transparent medium being an adhesive material; the input optical system is configured to receive light from a light source and includes a wavefront shaping device configured to collimate the received light in only one plane, the wavefront shaping device being configured such that the one plane passes through a cylindrical axis of the cylindrical waveguide; the cylindrical axis being the axis of rotational symmetry of the cylindrical waveguide; Glasses lenses.

2. The spectacle lens of claim 1 , wherein the first lens portion, the second lens portion, the cylindrical waveguide, and the transparent medium are arranged as an optical stack.

3. 3. The spectacle lens of claim 1 or 2, wherein the spectacle lens has a major axis and a minor axis, and the first and second cylindrical interfaces have a curved profile along the major axis.

4. The eyeglass lens of claim 3 , wherein the first and second cylindrical interfaces have a linear profile along the minor axis.

5. The spectacle lens of claim 1 , wherein the first lens portion and the second lens portion have a spherical outer profile.

6. The spectacle lens of claim 1 , wherein the input optics includes an input coupling linear grating having a constant period applied to a surface of the waveguide.

7. The spectacle lens of claim 6 , wherein the input coupling linear grating is attached to the waveguide at the first cylindrical interface or the second cylindrical interface.

8. The spectacle lens of claim 7 , wherein the input coupling linear grating is switchable.

9. 9. A spectacle lens according to claim 7 or claim 8, wherein the input coupling linear diffraction grating is formed from a holographic material.

10. 2. The spectacle lens of claim 1, wherein the input optics is constructed and arranged to receive light rays from an image source and direct the light rays into the cylindrical waveguide such that all light rays originating from the same pixel of the image source are incident on the surface of the cylindrical waveguide at each point of incidence at the same angle relative to a surface perpendicular to a common cylindrical axis and at the same angle relative to a plane perpendicular to the common cylindrical axis, whereby the coupled-in light retains its directional angle as it propagates along the cylindrical waveguide.

11. 10. The eyeglass lens of claim 1, further comprising output optics constructed and arranged to receive propagated light from the cylindrical waveguide and present the light as an image to an eye of a user.

12. The spectacle lens of claim 11 , wherein the output optics includes an output coupling linear grating having a constant period applied to a surface of the waveguide.

13. 13. The spectacle lens of claim 12, wherein the output coupling linear grating is attached to the waveguide at the first cylindrical interface or the second cylindrical interface.

14. The spectacle lens of claim 12 , wherein the output coupling linear grating is switchable.

15. The spectacle lens of claim 12 , wherein the output coupling linear grating is formed of a holographic material.

16. 1. A method for manufacturing a spectacle lens for an augmented reality display, the method comprising: forming a first lens portion and a second lens portion and interposing a cylindrical waveguide therebetween; forming a cylindrical waveguide having cylindrical concentric opposing surfaces for propagating light along a waveguide having rotational symmetry, the cylindrical concentric opposing surfaces defining a first cylindrical interface with the first lens portion and a second cylindrical interface with the second lens portion, the cylindrical waveguide being transparent and including a central waveguide core having a transparent medium at the first and second cylindrical interfaces, the central waveguide core having a higher refractive index than the transparent medium, the transparent medium being an adhesive material; forming an input optical system for coupling light into the cylindrical waveguide, the input optical system being configured to receive light from a light source and comprising a wavefront shaping device configured to collimate the received light in only one plane, the wavefront shaping device being configured to pass through a cylindrical axis of the cylindrical waveguide; Including, The method of claim 1, wherein the cylinder axis is an axis of rotational symmetry of the cylindrical waveguide.

17. The method of claim 16 , wherein the first lens portion, the second lens portion, the cylindrical waveguide, and the transparent medium are arranged as an optical stack.

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