Eyeglass lenses and wearable head-up displays

Abstract

The present disclosure relates to a spectacle lens for a wearable head-up display, the spectacle lens including a holographic optical element having an optical center, a main line of sight axis, and a vertex, the holographic optical element being integrated with the spectacle lens such that the vertex coincides with an image viewing axis along which digital content is viewable, the optical center of the lens being positioned relative to the main line of sight axis, and the vertex being positioned relative to the optical center. Also disclosed is a wearable display, the display including a spectacle lens, a spectacle frame, and an image light source, the spectacle lens mounted in the frame, and the image light source mounted on an arm portion of the frame adjacent to the spectacle lens to project light onto the holographic optical element of the spectacle lens to generate one or more image eyepoints.

Description

[Technical Field]

[0001] The present disclosure relates to eyeglass lenses integrated with holographic optical elements (HOEs) for use in wearable head-up displays (HUDs). More particularly, the present disclosure relates to eyeglass lenses in which the holographic optical elements are formed as thin films integrated with the eyeglass lenses. The present disclosure also relates to wearable HUD AR systems that include such eyeglass lenses. [Background technology]

[0002] Eyeglass lenses are typically manufactured using lens grinding or injection molding techniques. The eyeglass lens injection molding process involves injecting molten material under high pressure into a mold. The mold is formed with either a blank shape to create a lens "blank" whose inner surface is intended to be further shaped to create the final lens, or the exact contours of the desired eyeglass lens, including the inner and outer curvature profiles. After a short cooling period, the lens is completed. Due to the ease and speed of this process, injection molding is the technique of choice for large batches or stock lenses such as sunglasses. For more customized applications, lens grinding techniques are used. The lens grinding process begins with a lens "blank" that has a convex outer (world-facing) surface and either a flat or concave inner (eye-facing) surface. The curved surfaces of these blanks are typically spherical or spherocylindrical profiles. The inner surface is then ground to the desired curvature profile using specialized machines and then polished. The eyeglass lens is then edged to the desired edge profile to fit the frame, completing the eyeglasses. With the advent of 3D printing (or additive manufacturing) technology, it is even possible to 3D print eyeglass lenses with completely custom-made curvatures and edge profiles.

[0003] Integrating thin films with or encapsulating them within eyeglass lenses is desirable for many purposes. For example, some augmented reality (AR) systems (including associated eye-tracking systems) require holographic optical elements (HOEs) that can be fabricated on thin films that are affixed to or encapsulated in eyeglass lenses.

[0004] There are numerous existing approaches for integrating such thin films into or laminating them to eyeglasses. For example, U.S. Patent No. 6,269,949 details a process for directly laminating cellulose acetate laminate films to eyeglasses of various profiles for use in safety glasses. U.S. Patent No. 6,269,949 describes a number of integration techniques. In the first of these, the lens is injection molded, and a mold is created with a cavity into which the HOE photopolymer film is placed prior to casting. Eyeglass material is then injected into the mold, encapsulating the HOE inside. In a second technique, the HOE is encapsulated between two half-lenses, consisting of a rear and a front portion of the eyeglass lens. The HOE is sandwiched at the interface between the two eyeglass lens components or parts. In a third approach, the photopolymer film is laminated directly to the spherical, concave inner surface of the eyeglass lens.

[0005] In AR applications such as wearable HUDs, the integration and placement of the HOE and eyeglass lenses, as well as the alignment of the image source between the HOE and eyeglass lenses, are not trivial. The HOE must be carefully positioned to ensure that the generated image is incident on the user's eye (taking into account various physiological differences between users) and has good resolution and color uniformity.

[0006] Known approaches involve complex manufacturing techniques and carry the risk of misalignment of the HOE relative to the eyeglass lens into which it is integrated, relative to the user's pupil, and / or relative to the image light source, any misalignment potentially preventing or obstructing a user of the wearable HUD from fully or partially viewing the displayed content.

[0007] When a HUD requires strict focus at the eye, such as in virtual retinal displays or eye-tracking applications, especially in small-form-factor wearable HUDs, the smaller optical requirements of the light source necessitate a smaller eyebox (or eyepoint), typically ranging from 2 mm² to 5 mm², to support an adequate field of view. In AR HUD applications, the eyebox typically represents the volume of space in which a viewable image is formed. The eyebox represents a combination of exit pupil area, field of view, and eye relief (or back vertex distance (BVD)). The virtual image or displayed content is visible only when the user's pupils are in a specific position corresponding to the eyebox (or eyepoint) position. Outside the eyebox position, the virtual image or displayed content is partially occluded or not visible at all. Increasing the eyebox or sacrificing field of view can accommodate physiological differences such as IPD, wrap angle, and forward tilt angle among different users. However, this results in a larger and heavier HUD and requires a larger projection system and image calibration required to adjust the displayed image content for each user.

[0008] Alternatively, one way to increase eyebox size, for example in a VRD-based system, is to create multiple replicated eyeboxes or eyepoints such that a range of typical users' IPDs fit within at least one eyepoint. Additionally, the user's gaze direction, and therefore the positioning of the HOE, is important to consider when designing a HUD to ensure that the displayed content is fully viewable by the user. In the context of this disclosure, virtual image, displayed content, or other similar terms refer to digital content or images displayed to a user of a wearable HUD. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] US 2015 / 0131047 A1 [Patent Document 2] US 2017 / 0068095 A1 Summary of the Invention [Means for solving the problem]

[0010] According to a first aspect, there is provided a spectacle lens for a wearable head-up display, the spectacle lens comprising: a holographic optical element having an optical center, a main line of sight axis, and a vertex, the holographic optical element being integrated with the spectacle lens such that the vertex coincides with an image viewing axis through which digital content is viewable, the optical center of the lens being positioned relative to the main line of sight axis, and the vertex being positioned relative to the optical center.

[0011] The image viewing axis may be offset from the main viewing axis. The image viewing axis may be offset from the main viewing axis in the horizontal plane by a horizontal image viewing angle and in the vertical plane by a vertical image viewing angle.

[0012] The horizontal viewing angle may be defined as any angle between zero, defined by the primary gaze direction, and the maximum possible leftward or rightward horizontal rotation of the user's eyes. The vertical viewing angle may be defined as any angle between zero, defined by the primary gaze direction, and the maximum possible upward or downward vertical rotation of the user's eyes.

[0013] The horizontal image viewing angle may be between 0 and 40 degrees in adduction or abduction, preferably between 5 and 10 degrees in adduction or abduction, and the vertical image viewing angle may be between 0 and 28 degrees in elevation and between 47 degrees in descent, preferably between 5 and 10 degrees in elevation or descent.

[0014] The holographic optical element may include a first variation of the holographic feature constructed and arranged to compensate for horizontal and vertical image viewing angles offset from the primary line of sight axis. The first variation of the holographic feature may be a local variation of the surface grating pitch. The image viewing axis may be substantially coincident with the primary line of sight axis.

[0015] The optical center of the spectacle lens may be offset relative to the primary line of sight. The optical center of the spectacle lens may be offset relative to the primary line of sight and the apex of the holographic optical element may be offset relative to the optical center of the spectacle lens.

[0016] The optical center of the lens may be offset from the main line of sight axis by between 0 and 40 degrees, preferably between 5 and 10 degrees, and the vertex of the holographic optical element (and therefore the image viewing axis) may be offset from the optical center of the lens by between 0 and 40 degrees, preferably between 5 and 10 degrees.

[0017] The holographic optical element may include a second variation of the holographic function to compensate for the optical center of the lens being offset relative to the primary line of sight axis and to compensate for the vertex of the holographic optical element being offset relative to the optical center of the lens. The second variation of the holographic function may be a local variation of the surface grating pitch. The first and second variations of the holographic function may be variations of a phase gradient.

[0018] According to a second aspect, there is provided a wearable head-up display, the display comprising: an eyeglass lens according to the first aspect; an eyeglass frame; and an image light source, the eyeglass lens mounted in the frame and the image light source mounted on an arm portion of the frame adjacent the eyeglass lens to project light onto a holographic optical element in the eyeglass lens to generate one or more image eyepoints.

[0019] The one or more eyepoints may be generated symmetrically about the line of sight axis, or the one or more image eyepoints may be generated asymmetrically about the line of sight axis.

[0020] The angle of the chief ray from the image source relative to the holographic optical element may be constant. The vertex of the holographic optical element may be aligned with the chief ray of the image source so that the chief ray coincides with the vertex. The holographic optical element may be offset with respect to the intersection of the chief ray in air with the plane of the holographic optical element to account for refraction by the spectacle lens.

[0021] The image viewing axis may be offset from the main viewing axis in the horizontal plane by an amount equal to the wrap angle of the spectacle lenses mounted in the spectacle frame. The image viewing axis may be offset from the main viewing axis in the vertical plane by an amount equal to the forward tilt angle of the spectacle lenses mounted in the spectacle frame.

[0022] The first variation of the hologram function is the variation of the phase of the hologram function to compensate for the wrap angle and pretilt angle of the holographic optical element.

[0023] The eyeglass lens includes a first lens component formed on a second lens component with an interface therebetween; the holographic optical element may be interposed between the first and second lens components at the interface.

[0024] The interface may be a curved interface, the curved interface may be cylindrical, the spectacle lens may have a major axis and a minor axis, and the cylindrical interface may have a curved profile along the major axis and a linear profile along the minor axis. Alternatively, the curved interface may be spherical. The curved interface surface may contribute vertical and horizontal power, and the holographic optical element may be constructed and arranged to compensate for the vertical and horizontal power.

[0025] The configurations disclosed herein address one or more of the above problems, including, but not limited to, achieving an image viewing axis with good resolution and brightness for a range of users with physiological differences without sacrificing field of view, compactness, weight, or prescription range. By properly positioning the HOE with the spectacle lenses and positioning the HOE in combination with gaze direction, i.e., for different proposed gaze positions, there is minimal variation in the digital image content directed to the user's eye, which may otherwise be caused by variations in the distance from the HOE to the user's pupil, IPD, wrap and tilt angles, or other physiological factors related to the eyeglass and frame design. [Brief explanation of the drawings]

[0026] To enable a detailed understanding of the features of the present disclosure, a more detailed description will be provided 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 therefore should not be considered limiting of its scope. The drawings are intended to facilitate understanding of the disclosure and therefore are not necessarily drawn to scale. Advantages of the claimed subject matter will become 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 and are as follows:

[0027] [Figure 1a] FIG. 1 a shows a front view of a spectacle lens for use in a wearable head-up display (HUD) according to an embodiment; [Figure 1b] FIG. 1b shows a side view of the spectacle lens of FIG. 1a; [Figure 2a] FIG. 2a shows a spectacle lens including a holographic optical element with multiple eyepoints of the holographic optical element arranged symmetrically around the line of sight; [Figure 2b] Figure 2b shows the wrap angle of the spectacle lens of Figure 2a relative to the direction of the user's eyes; [Figure 3]FIG. 3 shows a spectacle lens including a holographic optical element with multiple eyepoints of the holographic optical element arranged asymmetrically around the line of sight; [Figure 4a] Figure 4a shows the forward tilt angle of the spectacle lens of Figures 1a and 1b relative to the user's pupil; [Figure 4b] Figure 4b shows an enlarged view of the spectacle lens shown in Figure 4a; [Figure 4c] FIG. 4c shows a side view of the spectacle lens of FIGS. 1a and 1b relative to the user's pupil; [Figure 5a] FIG. 5a shows a cross-sectional view of the spectacle lens of FIGS. 1a and 1b; [Figure 5b] Figure 5b is an exploded view of area A in Figure 5a; [Figure 6a] FIG. 6a shows a perspective view of a spectacle lens according to an embodiment; [Figure 6b] FIG. 6b shows a cross-sectional view of the spectacle lens of FIG. 6a; and [Figure 7a] FIG. 7 a shows an exploded perspective view of spectacle lens components according to an embodiment; [Figure 7b] FIG. 7b shows a perspective view of an eyeglass lens component according to an embodiment; [Figure 8] FIG. 8 shows the layer stacks of the front and rear lens components with a holographic optical element stack of multiple hologram layers therebetween; and [Figure 9] FIG. 9 shows an AR system in the form of AR glasses including eyeglass lenses according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0028] Before describing the embodiments of the present disclosure, it is necessary to define some common optometric terms that will be used throughout this specification.

[0029] The term primary gaze axis / direction is defined as the user looking straight ahead at a point on the horizon at infinity. The location of the lens optical center relative to the primary gaze direction can affect the user's visual acuity and ocular alignment when wearing the eyeglasses.

[0030] The term tilt angle (or simply "tilt") defines the angle in a vertical plane relative to the primary gaze axis / direction. More specifically, it is the intersection of the primary gaze axis / direction with the lens plane. It is determined by measuring the angle between the vertical axis of the eyeglass frame and the corneal plane, an imaginary plane that passes through the center of the user's eye. A tilt angle that is too steep can cause eye strain and discomfort for the user, while a tilt angle that is too shallow can cause the frame to slip down the nose and obstruct vision. In AR applications, the tilt angle can be between 0 and 20 degrees, depending on the frame design.

[0031] Frame wrap (or simply "wrap") is an angle that represents the horizontal angle of the lens plane relative to the primary line of sight / direction. It is determined by measuring the angle between the vertical axis of the eyeglass frame and an imaginary plane passing through the center of the lens. The wrap angle can affect the amount of peripheral vision the lens provides. A higher wrap angle can provide more coverage of peripheral vision, which may be beneficial for certain activities such as sports or driving. However, a higher wrap angle can also make the lens appear larger and more prominent, which may not be desirable for all users. In AR applications, the wrap angle can be between 0 and 20 degrees, depending on the frame design.

[0032] The term interpupillary distance (IPD) is the distance measured in millimeters between the centers of the pupils of each eye. IPD varies from 42 mm to 75 mm in the human population.

[0033] The term spectacle plane is defined by both the lap and the slope of the frame design. The optical axis is perpendicular to the spectacle plane and passes through the optical center of the spectacle lens. In this context, the optical center of the lens is the point at which light rays pass through the lens without deviation. In concave corrective lenses, this is usually the thinnest part of the lens.

[0034] The term eye relief (also known as back vertex distance or BVD) refers to the distance along the primary line of sight between the pupil and the spectacle plane. In the discussion of the following embodiments, the spectacle plane is the same as the plane of the holographic optical element integrated with the spectacle lens.

[0035] The term line of sight offset refers to the angular offset from a primary line of sight axis along which displayed content is viewable. Those skilled in the art will understand that the line of sight offset can be zero, in which case it will substantially coincide with the primary line of sight direction. More generally, when the included angle between two axes is given as zero, those skilled in the art will understand that this means that the axes or points on the axes coincide.

[0036] 1a and 1b show a front view and a top cross-sectional view, respectively, of an embodiment of a spectacle lens 100 integrated with a holographic optical element (HOE) 102 suitable for use in a wearable head-up display (HUD). The spectacle lens 100 may be of any suitable shape, the shape being largely determined by the design and contours of the eyeglass frame into which the spectacle lens 100 will be mounted (see, for example, FIG. 9). Suitable shapes of spectacle lenses 100 integrated with a holographic optical element (HOE) 102 are manufactured from pre-formed lens blanks or "pucks," as discussed in more detail below.

[0037] The eyeglass lens 100 includes an optical center 104 and a geometric center 106. The optical center of a lens is the point where the interface between the lens material and air is parallel and where light rays pass through the lens without deflection. It is the thinnest part of a concave lens. As shown, the geometric center 106 of the lens may coincide with the optical center 104 of the lens. However, the geometric center 106 of the lens may not coincide with the optical center 104 of the lens. Whether the geometric center 106 coincides with the optical center 104 depends on the shape of the lens in the frame, i.e., how the lens is formed from a lens blank to fit into the frame (known as glazing). This is typically a design choice based on the wrap angle, tilt angle, and content direction (image viewing direction).

[0038] When mounted in an eyeglass frame, the optical center 104 of the eyeglass lens may generally coincide with the pupil of the user's eye based on the user's IPD. This is particularly important when the eyeglass lens has corrective optical power to correct the user's prescription. Thus, depending on the particular user's IPD and how the eyeglass lens 100 is cut from the lens blank, the optical center 104 may not coincide with the geometric center 104 of the eyeglass lens 100. For zero prescription lenses for AR applications, the user's IPD determines the optimal position of the HOE.

[0039] The principal viewing direction (or axis) is defined as the axis PP from the user's eye through the spectacle lens 100 when the user is looking straight ahead toward the distant horizon with no head tilt. The HOE 102 also includes a geometric center and apex, which may or may not coincide. The apex of the HOE is defined by a reference pixel corresponding to the central pixel where the virtual or digital image content is viewable and is the point where the chief ray from the image light source enters the HOE. The apex may also be defined with respect to a reference pixel of the projected image to which all other pixels are calibrated. Based on the known position of the holographic optical element, the apex is positioned so that the image viewing axis is achieved.

[0040] The apex of the HOE 102 is substantially aligned with or coincides with a gaze offset direction, also known as the image viewing axis II. In augmented reality applications, it may be desirable for the digital image content to be offset from the primary gaze direction PP so that the display of the digital image content does not interfere with the user's view of the world along the primary gaze direction. In this case, the apex of the HOE 102 is offset from the primary gaze axis of the spectacle lens 100 so that the digital content is not visible when the user looks through the spectacle lens in the primary gaze direction. The display of the digital image content viewable along the image viewing axis II is offset from the primary gaze direction PP by a horizontal and / or vertical angular offset, such that the digital image content is offset by a gaze offset θ as shown in FIG. 1b. GO1b illustrates a horizontal gaze offset, and those skilled in the art will appreciate that the gaze offset may also have an angle in the vertical direction. The gaze offset axis may be defined by a horizontal and / or vertical angle relative to the primary gaze direction. The gaze offset may also be defined by polar and azimuthal coordinates relative to the primary gaze axis and a tangent plane of the lens surface perpendicular to the primary gaze axis. The gaze offset may also be defined by the maximum horizontal rotation (maximum condition) of the user's eyes relative to the primary gaze axis (minimum condition). Thus, the gaze offset is the angular offset from the primary gaze axis along which digital content is viewable, and may intersect the HOE 102 at a different point than the primary gaze axis. Similarly, in certain augmented reality applications, it may be desirable for the gaze offset direction to coincide with the primary gaze direction. In this case, the digital content can be viewed in the primary gaze direction when the user looks through the eyeglass lens 100. Thus, the maximum limit of gaze offset direction is defined by the maximum rotation of the user's eyes from the primary gaze position, which, based on a human eyeball of approximately 25 mm, may be approximately ±40 degrees horizontally (adduction or abduction), 28 degrees elevation, and 47 degrees depression. Those skilled in the art will appreciate that sustained eye rotation to the maximum limits for extended periods of time may be uncomfortable for some users. Therefore, the horizontal and vertical image viewing angles are preferably no greater than approximately 12 degrees, and more preferably between approximately 4 and 11 degrees, with the 4-degree lower limit ensuring that digital image content is not positioned in the primary gaze direction, which may be distracting to the user.

[0041] The multiple eyepoints (or eyeboxes) may be arranged in a spaced pattern, such as a grid pattern, a linear array, or an n x m array (n and m are positive integers). The multiple eyepoints may be arranged symmetrically about the line of sight axis II (the so-called symmetric condition), as shown in Figures 2a and 2b and discussed in more detail below. Alternatively, the multiple eyepoints may be arranged asymmetrically about the line of sight axis II (the so-called asymmetric condition), as shown in Figure 3 and discussed in more detail below. Alternatively, a single eyepoint defining the entire eyebox may be positioned to coincide with or offset from the line of sight axis II.

[0042] As described above, FIGS. 2a and 2b illustrate a symmetrical arrangement of multiple eyepoints 108 according to an embodiment. As shown in FIG. 2a, each eyepoint 108 is symmetrically arranged around the vertex of the HOE 102, with the geometric center of the HOE substantially coinciding with the optical center 104 of the spectacle lens 100. The geometric center 106 of the lens is also shown. The multiple eyepoints 108 may be symmetrically arranged around the optical center 104 of the spectacle lens 100; because the optical center of the spectacle lens coincides with the gaze offset direction, the multiple eyepoints are symmetrically arranged around this axis II (reference numeral 112 in FIG. 2b). While FIG. 2a illustrates four eyepoints 108, those skilled in the art will understand that any number of eyepoints 108 can be used as long as they are symmetrically arranged. Those skilled in the art will also understand that the eyepoints 108 are spaced apart to define effectively replicated eyebox areas within which a user can view digital image content.

[0043] FIG. 2b is a top view illustrating the lens wrap, showing the spectacle lens 100 and HOE 102 of FIGS. 1a-2b positioned relative to a user's eye. The primary gaze axis PP is indicated by axis 110 from the eye's pupil to the vertex of the HOE 102. The gaze offset direction 112 is indicated by axis II. By way of example, the gaze offset direction 112 can be any angle determined by the maximum comfortable rotation of the user's eye. A light beam 114 from an image source 116 enters the holographic optical element 102 at the vertex. The chief ray from the image source 116 enters the HOE at an angle determined by the position of the image source relative to the HOE and the maximum achievable numerical aperture of the HOE. For example, the angle of the chief ray from the image source 116 may be 56 degrees at the vertex of the HOE relative to the surface normal of the HOE. A typical wrap angle for spectacle lenses may be between 0 and 20 degrees. Beamlets 118, 118' are deflected from projector beam 114 by holographic optical element 102 and pass through the pupil of the user's eye onto the retina of the eye, forming a collimated eyepoint 108 at the pupil of the user's eye.

[0044] As shown in FIG. 3, each eyepoint 108 is asymmetrically positioned around the vertex (and axis II) of the HOE 102. Therefore, the multiple eyepoints 108 are asymmetrically positioned around the line of sight. While FIG. 3 shows four eyepoints 108, those skilled in the art will understand that any number of eyepoints 108 can be used, as long as they are asymmetrically positioned. Similar to the symmetrical arrangement described above, those skilled in the art will also understand that the eyepoints 108 can be spaced apart to define effectively replicated eyebox regions in which a user can view digital image content. By way of example, the line of sight offset direction can be any angle depending on the maximum comfortable rotation of the user's eyes. A projector beam 114 from an image source 116 is incident on the holographic optical element 102 as described above.

[0045] In FIGS. 4a and 4b, which illustrate the concept of forward tilt angle of the spectacle lens 100 according to the embodiment, the main gaze direction is indicated by axis 402, the gaze offset direction is indicated by axis 404, and the forward tilt angle is the angle θ between the main gaze axis 402 and the normal at the pupil center to the rear surface of the spectacle lens. tilt Variations in this distance, also known as the posterior vertex distance (BVD), can change the field of view (FOV) or the size of the viewable digital image content. Large variations in BVD can cause image clipping, image shifting, or reduced image brightness. Here, BVD is measured from the pupil center to the holographic optical element center 104. The gaze offset axis is positioned to coincide with the anterior tilt angle. Positioning the holographic optical element 102 vertex relative to the gaze offset direction 112 minimizes changes in beamlet position on the retina caused by small changes in the distance from the holographic optical element 102 to the user's eye pupil. BVD is inversely related to FOV for a given HOE area.

[0046] In FIG. 4c, which shows the wrap angle of the spectacle lens 100 according to the embodiment, the main gaze direction is indicated by axis 402, the gaze offset direction is indicated by axis 404, and the wrap is determined by the angle θ between the main gaze axis 402 and the wrap. wrap Forward tilt angle θ tilt Similarly, the horizontal gaze offset angle may correspond to the wrap angle. In this way, the optical center of the spectacle lens 100 is aligned with the apex of the holographic optical element 102. The alignment of the forward tilt angle and wrap angle is further shown in FIG. 4d. The optical center of the spectacle lens 100 coincides with the wrap and tilt offset point 406. Typical tilt angles for spectacle lenses may be between 0 and 20 degrees.

[0047] The image viewing axis is offset from the primary line-of-sight axis by a horizontal image viewing angle in the horizontal plane and a vertical image viewing angle in the vertical plane. The horizontal and vertical image viewing angles are limited by the maximum rotation of the eye. In this case, the holographic optical element may include a first variation of the holographic feature constructed and arranged to compensate for the horizontal and vertical image viewing angles being offset from the primary line-of-sight axis. The first variation of the holographic feature is formed by a local variation of the surface grating pitch when recording the holographic feature. The variation of the surface grating pitch may be a variation of a local phase gradient. Similarly, the variation of the holographic feature may be achieved by a variation of the fringe spacing in the bulk or volume of the holographic material of the HOE.

[0048] The optical center 104 of the spectacle lens 100 may be offset relative to the primary line of sight axis PP, and the apex of the holographic optical element 102, and therefore the image viewing axis, is offset relative to the optical center 104 of the spectacle lens 100. The optical center of the spectacle lens 100 is offset relative to the primary line of sight axis by between 0 and 20 degrees, preferably between 4 and 11 degrees, and the apex of the holographic optical element is offset relative to the optical center of the lens by between 0 and 20 degrees, preferably between 4 and 11 degrees.

[0049] The holographic optical element 102 may include a second variation of the holographic feature to compensate for the offset of the optical center 104 of the spectacle lens 100 relative to the primary line of sight axis and to compensate for the offset of the vertex of the holographic optical element 102 relative to the optical center of the spectacle lens 100. This second, further variation of the holographic feature is formed by a local variation of the surface grating pitch when recording the holographic feature. The further variation may be the surface grating pitch, which is a variation of the phase by changing the local grating gradient. The further variation takes into account the shape of the world-side and eye-side surfaces of the spectacle lens.

[0050] The image viewing axis is offset from the main line of sight axis in the horizontal plane by an amount equal to the wrap angle of the spectacle lens 100 mounted in the spectacle frame (discussed below with respect to FIG. 9). Similarly, the image viewing axis is offset from the main line of sight axis in the vertical plane by an amount equal to the forward tilt angle of the spectacle lens 100 mounted in the spectacle frame. Thus, one skilled in the art will understand that the first variation of the holographic feature compensates for the wrap angle and forward tilt angle of the holographic optical element integrated with the spectacle lens, and is the variation of the phase of the holographic feature when the spectacle lens 100 is mounted in the spectacle frame.

[0051] 5a, when the holographic optical element 102 is embedded in the eyeglass lens 100, it is necessary to align the angle of the beam of light 114 from the projector 116 to compensate for the refractive index and thickness of the eyeglass lens 100 material. The projector beam angle θ Proj Based on the following equation (which is the angle between the projector beam and the local surface normal 120 to the point on the spectacle lens 100 where the light beam enters the spectacle lens at the eye-side surface 122), the refractive index of the spectacle lens material being 1.5, and the lens material thickness being 1.6 mm, an adjustment is made to the position X between the nominal front position and the point where the chief ray from the projector 116 (the projector beam 114) enters the eye-side surface of the spectacle lens. More broadly, and in accordance with the above, those skilled in the art will understand that it is not possible to align the vertex of the holographic optical element 102 at the center of rotation so that the beam 114 from the projector 116 hits the vertex. Figure 5b is an exploded view of region A in Figure 5a. The holographic optical element includes an optical function that compensates for the curvature of the lens surface where the beam light 114 from the projector 116 enters the lens and also compensates for the refractive index of the lens material. This optical function adjusts the angle of incidence θ depending on the refractive index and thickness of the lens material. Inc If this compensation is not included, the light beam will not be incident on the vertex of the holographic optical element.

[0052] For the above refractive index of 1.5 and thickness of 1.6 mm, if refraction of the beam 114 from the projector 116 is not taken into account, a displacement X of up to 1.07 mm can occur relative to the unrefracted beam 114.

[0053] The spectacle lens according to the embodiment can embed a holographic optical element within the spectacle lens material by any suitable process. For example, FIG. 6a shows that a holographic optical element (not shown for clarity) is encapsulated within the spectacle lens 100 by forming the spectacle lens from two components, with the interface between the two components having a cylindrical profile. The holographic optical element may be formed from a thin film material, such as a photopolymer or silver halide. While thin film parameters are generally well understood, in this context, the thin film (e.g., a photopolymer thin film or a silver halide thin film) may have a thickness on the order of 100 microns or less. This is typically a low-absorption, optically transparent (or clear), low-haze film suitable for incorporation into a lens without significantly affecting see-through visibility. A central reference plane 202 of the spectacle lens in the xz plane is highlighted. See also FIG. 6b, which shows a cross-section of the spectacle lens of FIG. 6a at the reference plane 202. Here, the cylindrical interface profile 203 between the two components is indicated by a dotted line.

[0054] The two components are usually manufactured separately, but may also be formed from a split eyeglass lens. Cylindrical surfaces on the lens or lens components are not typical. The cylindrical surface between the two lens components can be created by grinding or a custom mold (injection molding). Optionally, 3D printing can also be used to create the lens components. Manufacturing lens components with a cylindrical interface is not a standard technique. Nevertheless, it is possible using injection molding (e.g., of plastic), grinding, or 3D printing. Standard lens grinding and mold manufacturing may use diamond turning, which usually means a spherical surface, but this and other techniques can be used to achieve a cylindrical surface instead.

[0055] Referring now to FIG. 7a, the components of the spectacle lens of FIG. 6a are depicted. These include: a first component 701 (incorporating the eye-side surface); and a second component 702 (incorporating the world-side surface). The interface between the first component 701 and the second component 702 has a cylindrical shape (as shown in FIG. 6b), curved (in this case, a circular arc segment) in the x-z plane, and flat in the y-z plane (and also flat in the x-y plane). A holographic optical element (not shown in FIG. 7a) of the same size as the x- and y-dimensions and profile of the eyeglasses is laminated onto the cylindrical interface between the first component 701 and the second component 702. When the first component 701 and the second component 702 are attached to each other, the holographic optical element is fully encapsulated within the spectacle lens. Lamination on a cylindrical surface avoids the deformations associated with lamination on a spherical surface. The interface is preferably purely cylindrical, but may also be partially spherocylindrical or toric, as long as the deviation from a purely cylindrical shape at the HOE location is negligible. The closer the interface is to a perfect cylinder, the more the stresses within the thin film are minimized.

[0056] As noted above, the cylindrical interface between the first component 701 and the second component 702 is flat in one axis. Therefore, this axis presents the same geometric constraints as using a flat thin film. However, because eyeglass lenses typically have a significant aspect ratio, this constraint is less important when applied only to the short (minor) axis of the eyeglass lens. This is discussed in more detail below. Attaching the thin film to one cylindrical surface of the lens component can be achieved in a number of ways. Thin film lamination may not require bonding to one or both surfaces of the cylindrical interface (the first component 701 and the second component 702 may simply be attached to each other with the thin film sandwiched between them), although additional bonding may be provided. The HOE may be a photopolymer, such as Bayfol (RTM) HX (sold by Covestro AG), which typically has a substrate thickness of about 60 microns and a polymer layer thickness of about 20 microns. One side of the photopolymer is then typically an adhesive film that adheres to glass or plastic when laminated to a surface using a roller (or similar). Alternatively or additionally, adhesives, double-sided tape, vacuum, heat, or pressure treatments can be used to adhere the HOE to the substrate. The HOE can instead be a silver halide film, and the above techniques can be used to adhere the thin film to the substrate surface. The choice of lens material can aid in adhesion; for example, polycarbonate may provide better adhesion. Thin films typically do not extend all the way to the edge of the cylindrical interface. This may allow for better encapsulation (no moisture ingress) if there is a good adhesive seal around the perimeter.

[0057] Referring to Figure 7b, there is shown a schematic representation of an eyeglass lens 100 assembled from the components of Figure 7a, and also showing a thin film 104 encapsulated between a first component 701 and a second component 702. The completed eyeglass lens 703 is therefore made by two components joined by a cylindrical interface with the thin film 704 between them.

[0058] The eye-side component (first component 701) may be molded in the desired shape of the eyeglass lens. More typically, it is molded as a lens blank, which has a cylindrical profile on the anterior surface (which is bonded to the world-side component 702), while the posterior surface may be flat or have any surface curvature. The first component 701, second component 702, and thin film 104 are then bonded to form the eyeglass lens 100 as a lens "blank" with an embedded HOE.

[0059] Once the assembled eyeglass lens 100 is formed in this manner, it appears as a lens blank with a circular profile, and the rear surface can be ground as a standard lens blank to produce the final lens. To fit into eyeglasses, the curvature of the front and rear surfaces is typically edged (ground around the edges) to fit into the eyeglass frame. This process can be performed on the first component 701 and the second component 702 before thin-film encapsulation and assembly, or after assembly. The grinding process, in which the front and / or rear surfaces are ground into a curvature, is a more aggressive process than edging, and if necessary, it is preferably performed on the first component 701 and / or the second component 702 before thin-film encapsulation and assembly.

[0060] Thus, the world-side component is usually formed to include a front surface, typically spherical, with the desired base curvature, and a rear surface with a cylindrical profile. The eye-side component may also be formed to include a front surface and a rear surface with a cylindrical profile. This rear surface may be formed with the desired curvature of the final prescription. Alternatively, the rear surface can be left flat (or of any curvature) to create a lens blank, and further grinding of this surface can be used to set the prescription.

[0061] The holographic optical element may be configured to function as a planar mirror. In this case, the holographic optical element may not add optical power itself. The total optical power of the holographic optical element may be determined by the cylindrical curvature of the inner surface to which the HOE is laminated. An eyeglass lens exhibits optical power relative to the real world determined only by the curvatures of the inner and outer surfaces of the eyeglass lens. Alternatively, the eyeglass lens may be configured such that the total optical power of the holographic optical element is determined by the sum of the optical power of the hologram of the holographic optical element and the optical power due to the curvature of the cylindrical interface. In this case, the HOE may function as a reflective power optical element (typical in AR applications). The holographic optical element may be a photosensitive material, and a hologram may be recorded on the photosensitive material to form the holographic optical element. In certain cases, recording a hologram on the photosensitive material may include providing the photosensitive material on a planar substrate; and recording a hologram on the photosensitive material while it is on the planar substrate, where the hologram is recorded to compensate for the optical power of the cylindrical interface. This provides a holographic optical element, which may then be applied to the cylindrical interface. In other cases, recording the hologram on the photosensitive material may include: applying the photosensitive material to a cylindrical interface; and recording the hologram on the photosensitive material while it is on the cylindrical interface. In other cases, the projector or image light source may be compensated, rather than the hologram.

[0062] Regarding optical power compensation, the rear surface of a spectacle lens, i.e., the surface facing the eye, is the most important for holographic optical element function. The effective curvature of the rear surface of a spectacle lens is composed of optical power components in both the horizontal and vertical planes, with different powers at these planes. The total optical power of the rear lens portion is equal to the sum of the optical power due to the spherical curvature on the eye-facing side, the optical power due to the cylindrical curvature of the eye-facing portion of the spectacle lens, and the rear center thickness. To avoid astigmatism due to an eyepoint that is too far or too close to the holographic optical element, it is necessary to record holographic features on the holographic optical element to compensate for the total optical power. For example, the optical power due to the spherical curvature on the eye-facing side and the cylindrical power on the world-facing side can contribute -4D vertically and +8.9D horizontally.

[0063] An eyeglass lens according to an embodiment may include a holographic optical element 102 including a stack of holographic layers HOL1 and HOL2 between two lens components, as shown in FIG. 8. The stack of holographic layers HOL1 and HOL2 includes multiple holographic layers. While FIG. 8 shows two holographic layers HOL1 and HOL2, those skilled in the art will understand that any number of holographic layers HOL1 and HOL2 may be included depending on the particular application. For example, one or more of the holographic layers may be visible wavelength holograms. One or more of the holographic layers may be infrared (IR) wavelength holograms. IR holograms may be used when eye tracking needs to be implemented in an AR system.

[0064] When there are multiple hologram layers that make up a holographic optical element, it is necessary to align the holograms with respect to each other and with respect to the lens. This process is known as alignment. To accomplish this, those skilled in the art will understand that a system of alignment marks or fiducials can be used to align adjacent hologram layers with each other, and also to align the stack of hologram layers with the eyeglass lens components according to the embodiments described above.

[0065] As mentioned above, the eyeglass lens 100 may be of any suitable shape, with the shape being largely determined by the design and contours of the eyeglass frame in which the eyeglass lens 100 will be mounted. The required shape of the eyeglass lens 100 integrated with the HOE 102 may be cut or ground from a lens blank or "puck." Alternatively, the eyeglass lens or components of the eyeglass lens may be injection molded and / or overcast.

[0066] FIG. 9 illustrates an augmented reality system including at least one of the eyeglass lenses described above. The augmented reality system may take the form of a wearable head-up display, such as glasses 900. Similar to known types of eyeglasses, the eyeglasses 900 according to the embodiment include a frame 902. The frame includes arms 904 and lens mounting portions 906 connected by a bridge portion 908. One of the arms 904 includes a mounting portion 910 to which a projector (as described above) is fixedly mounted, such that the beam 114 from the projector 116 (not shown in FIG. 9 ) impinges on the eyeglass lens 100 according to the embodiment. Those skilled in the art will appreciate that the projector 116 is mounted on the arm 904 adjacent to the lens mounting portion 906 that holds the eyeglass lens 100 according to the embodiment. A standard ophthalmic lens may be inserted in the other lens mounting portion. Alternatively, an eyeglass lens according to the embodiment may be mounted in the other lens mounting portion, and an additional projector system 116 may be mounted in the corresponding mounting portion of the arm 904.

[0067] One or both of the arms 904 may be adapted to house a battery (not shown) that powers the projector described above. Additionally, one or both of the arms 904 may include control electronics (not shown) for controlling the operation of the projector 116. The projector may be a MEMS-based projector system or a pixelated projection system, such as a LOCOS, microLED, or OLED-based system. Additionally, the operation of the projector may be controlled via the control electronics by an eye-tracking system (not shown). The eye-tracking system may include a non-visible light source, such as an infrared LED, aimed at the user's eye and a light sensor positioned to capture the non-visible light reflected by the user's eye. The embodiments described herein apply equally to waveguide- or free-space-based AR systems.

[0068] Particular and preferred aspects of the present disclosure are set out in the accompanying independent claims. Combinations of features from the dependent and / or independent claims may be combined as appropriate and not solely as set out in the claims.

[0069] The scope of the present disclosure includes any novel feature or combination of features thereof, or generalization thereof, either explicitly or implicitly disclosed, whether or not it is related to the claimed disclosure or alleviates some or all of the problems addressed by the present disclosure. The applicant hereby gives notice that new claims may be formulated to such features during prosecution of this application or any further application derived therefrom. In particular, with reference to the appended claims, features from the dependent claims may be combined with features of the independent claims, and features from each independent claim may be combined in any suitable manner, not just in the specific combinations recited in the claims.

[0070] Features that are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

Claims

1. A spectacle lens for a wearable head-up display, the spectacle lens includes a holographic optical element having an optical center, a principal line of sight axis, and a vertex; the holographic optical element is integrated with the eyeglass lens such that the vertex coincides with an image viewing axis that makes digital content visible; the optical center of the lens is positioned relative to the primary line of sight axis, and the vertex is positioned relative to the optical center; Eyeglass lenses.

2. 10. The eyeglass lens of claim 1, A spectacle lens, wherein the image viewing axis is offset from the primary line of sight axis.

3. 3. The eyeglass lens according to claim 2, A spectacle lens, wherein the image viewing axis is offset from the main viewing axis in a horizontal plane by a horizontal image viewing angle and in a vertical plane by a vertical image viewing angle.

4. 4. The eyeglass lens according to claim 3, the horizontal image viewing angle is between 0 and 40 degrees in adduction or abduction, preferably between 4 and 12 degrees; the vertical image viewing angle is between 0 and 28 degrees in the up position and between 47 degrees in the down position, preferably between 4 and 12 degrees; Eyeglass lenses.

5. 10. The eyeglass lens of claim 1, the holographic optical element includes a first variation of a holographic feature constructed and arranged to compensate for the horizontal image-viewing angle and the vertical image-viewing angle being offset from a primary line-of-sight axis.

6. 6. The eyeglass lens according to claim 5, the first variation of the holographic function is a local variation of the surface grating pitch and / or fringe spacing within the holographic material of the holographic optical element; Eyeglass lenses.

7. 10. The eyeglass lens of claim 1, the image viewing axis is substantially aligned with the primary line of sight axis; Eyeglass lenses.

8. 10. The eyeglass lens of claim 1, the optical center of the lens is offset with respect to the primary line of sight axis; Eyeglass lenses.

9. 10. The eyeglass lens of claim 1, the optical center of the spectacle lens is offset with respect to the primary line of sight; the vertex of the holographic optical element is offset with respect to the optical center of the eyeglass lens; Eyeglass lenses.

10. 10. A spectacle lens according to any of the preceding claims, the optical center of the lens is offset from the primary line of sight axis by between 0 and 20 degrees, preferably between 5 and 10 degrees; the vertex of the holographic optical element is offset from the optical center of the lens by between 0 and 20 degrees, preferably between 5 and 10 degrees; Eyeglass lenses.

11. 10. A spectacle lens according to any of the preceding claims, the holographic optical element includes a second variation of a hologram function to compensate for the optical center of the lens being offset with respect to the primary line of sight axis and to compensate for the vertex of the holographic optical element being offset with respect to the optical center of the lens; Eyeglass lenses.

12. 12. The spectacle lens according to claim 11, the second variation of the hologram function is a local variation of the surface grating pitch; Eyeglass lenses.

13. 12. The spectacle lens according to claims 6 and 11, the first variation and the second variation of the holographic function are variations in phase gradient; Eyeglass lenses.

14. A wearable head-up display, A spectacle lens according to any one of claims 1 to 13, a spectacle frame, and an image light source, The eyeglass lenses are mounted in a frame, the image light source is mounted on an arm portion of the frame adjacent to the eyeglass lens to project light onto the holographic optical element of the eyeglass lens to generate one or more image eyepoints; Wearable head-up display.

15. 15. The wearable head-up display of claim 14, A wearable head-up display, wherein the one or more eye points are generated symmetrically around a line of sight axis.

16. 15. The wearable head-up display of claim 14, one or more of the image eyepoints are generated asymmetrically about the line of sight axis; Wearable head-up display.

17. 17. A wearable head-up display according to claim 14, wherein: the angle of the chief ray from the image light source relative to the holographic optical element is constant; Wearable head-up display.

18. 18. A wearable head-up display according to claim 14, wherein: The vertex of the holographic optical element may be aligned with the chief ray of the image light source such that the chief ray coincides with the vertex. Wearable head-up display.

19. 19. A wearable head-up display according to claim 14 to 18, the holographic optical element may be offset with respect to the intersection of the chief ray in air with the holographic optical element plane to take into account refraction by the spectacle lens; Wearable head-up display.

20. 20. A wearable head-up display according to claim 14 to 19, the image viewing axis is offset from the main line of sight axis in the horizontal plane by an amount equal to the wrap angle of the spectacle lens mounted in the spectacle frame; Wearable head-up display.

21. 21. A wearable head-up display according to claim 14 to 20, the image viewing axis is offset from the main line of sight axis in the vertical plane by an amount equal to the forward tilt angle of the spectacle lenses mounted in the spectacle frame; Wearable head-up display.

22. 22. A wearable head-up display according to claim 14 to 21, the first variation of the holographic feature is a variation of the phase of the holographic feature to compensate for the wrap angle and the pretilt angle of the holographic optical element; Wearable head-up display.

23. 14. A spectacle lens according to claim 1, the spectacle lens includes a first lens component formed on a second lens component with an interface therebetween, and the holographic optical element is interposed between the first lens component and the second lens component at the interface. Eyeglass lenses.

24. 24. The spectacle lens of claim 23, the interface is a curved interface; the curved interface is cylindrical; the spectacle lens has a major axis and a minor axis; the cylindrical interface having a curved profile across the longitudinal axis; having a linear profile across the minor axis; Eyeglass lenses.

25. 25. The spectacle lens of claim 24, a curved interface surface contributing vertical and horizontal power to said spectacle lens; the holographic optical element is constructed and arranged to compensate for the vertical and horizontal power of the lens; Eyeglass lenses.

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