Spectacle lens with holographic optical element

Abstract

The present disclosure relates to an ophthalmic lens for a wearable head-up display, the ophthalmic lens comprising: an optical center, a primary gaze axis, and a holographic optical element having an apex wherein the holographic optical element is integrated with the ophthalmic lens such that the apex coincides with an image viewing axis to allow viewing of digital content, and wherein the optical center of the lens is positioned relative to the primary gaze axis and the apex is positioned relative to the optical center. Also disclosed is a wearable display comprising an eyeglass lens mounted in the frame, an eyeglass frame, and an image source mounted on an arm of the frame adjacent to the eyeglass lens to project light onto a holographic optical element of the eyeglass lens to generate one or more image eyespots.

Description

Technical Field

[0001] The present disclosure relates to an eyeglass lens integrated with a holographic optical element (HOE) for use in a wearable head-up display (HUD). More specifically, the present disclosure relates to such an eyeglass lens, wherein the holographic optical element is formed by a thin film integrated with the eyeglass lens. The present disclosure also relates to a wearable HUD AR system incorporating such an eyeglass lens. Background Art

[0002] Eyeglass lenses are typically manufactured using lens grinding or injection molding techniques. The injection molding process for eyeglass lenses involves injecting molten material into a mold under high pressure. The mold is either shaped to create a lens "blank" with the intention of further shaping the inner surface to create the final lens, or it is formed with the precise contours of the desired eyeglass lens, including the inner and outer curvatures. After a short cooling period, the lens is finished. Due to its simplicity and speed, injection molding is the preferred technology for large-volume and stock lenses, such as sunglasses. For more customized applications, lens grinding techniques are used. The lens grinding process begins with a lens "blank" with a convex outer (world-facing) surface and a flat or concave inner (eye-facing) surface. The curved surface of these blanks is typically spherical or sphero-cylindrical in profile. Specialized machinery is then used to grind the inner surface to the desired curvature profile, followed by polishing. The eyeglass lens is then edged to the desired edge profile to fit the frame, completing the eyeglass. With the advent of 3D printing (or additive manufacturing) technology, it is also possible to 3D print eyeglass lenses with completely customized curvatures and edge profiles.

[0003] Integrating films with eyeglass lenses, or encapsulating them within eyeglass lenses, is ideal for many purposes. For example, some augmented reality (AR) systems (including related eye tracking systems) require holographic optical elements (HOEs), which can be produced on films that are then adhered to or encapsulated within eyeglass lenses.

[0004] There are many existing methods for integrating such films into glasses or laminating films onto glasses. For example, US2015 / 0131047A1 describes in detail a process for directly laminating cellulose acetate laminated films onto glasses of different contours for use in safety glasses. US2017 / 0068095 A1 describes a variety of integration techniques. In the first technique, the lens is manufactured by injection molding, in which a mold with a cavity is made to position the HOE photopolymer film before casting. The eyeglass material is then injected into the mold to encapsulate the HOE. The second technique encapsulates the HOE between two half-lenses, including the back portion of the eyeglass lens and the front portion of the eyeglass lens. The HOE is sandwiched at the interface of two eyeglass lens assemblies or components. In the third method, the photopolymer film is directly laminated onto the spherical concave inner surface of the eyeglass lens.

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

[0006] The known method involves complex manufacturing techniques and carries 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 may prevent or obstruct the user of the wearable HUD from fully or partially viewing the displayed content.

[0007] When the HUD needs to be tightly focused on the eye side, such as for virtual retinal displays or eye tracking applications, typically for small wearable HUDs, the eye box (or eye point) needs to be small to support sufficient field of view, typically around 2mm, due to the smaller optical requirements of the light source. 2 to 5mm 2 For AR HUD applications, the eye box typically describes the volume of space in which the visible image is formed. The eye box represents a combination of the exit pupil area, field of view, and eye distance (or back vertex distance BVD). The virtual image or display content can only be seen when the user's pupil is at a specific position corresponding to the position of the eye box (or eye point). Outside the eye box position, the virtual image or display content will be partially blocked or completely invisible. Increasing the eye box and / or sacrificing the field of view can accommodate physiological differences, such as the IPD, warp angle, and pantoscopic tilt angle of different users. However, this may make the HUD larger and heavier to accommodate the larger projection system and the image calibration required to adjust the displayed image content.

[0008] Alternatively, one way to increase the eyebox size is to generate multiple replicated eyeboxes or eyepoints, such as in a VRD-based system, so that for a range of typical users, the IPD range of these users will fall within at least one eyepoint. In addition, when designing a HUD, the user's gaze direction and therefore the positioning of the HOE are important factors to consider to ensure that the user can fully view the displayed content. In the context of this disclosure, virtual images, display content, or other similar terms refer to digital content or images displayed to the user of a wearable HUD. Summary of the Invention

[0009] According to a first aspect, there is provided a spectacle lens for a wearable head-up display, the spectacle lens comprising: an optical center, a primary gaze axis, and a holographic optical element having an apex, wherein the holographic optical element is integrated with the spectacle lens such that the apex coincides with the image viewing axis to allow viewing of digital content, and wherein the optical center of the lens is positioned relative to the primary gaze axis and the apex is positioned relative to the optical center.

[0010] The image viewing axis can be offset from the main gaze axis by a horizontal image viewing angle in the horizontal plane and by a vertical image viewing angle in the vertical plane.

[0011] The horizontal viewing angle can be defined as any angle between zero degrees, defined by the primary gaze direction, and the maximum horizontal rotation of the user's eyes to the left or right. The vertical viewing angle can be defined as any angle between zero degrees, defined by the primary gaze direction, and the maximum vertical rotation of the user's eyes to the up or down direction.

[0012] The horizontal image viewing angle can be between zero and 40 degrees in the adduction or abduction direction, preferably between 5 and 10 degrees in the adduction or abduction direction; the vertical image viewing angle is between zero and 28 degrees in the elevation direction and between 47 degrees in the depression direction, preferably between 5 and 10 degrees in the elevation or depression direction.

[0013] The holographic optical element may include a first variation in holographic functionality configured and arranged to compensate for horizontal and vertical image viewing angles that deviate from a primary viewing axis. The first variation in holographic functionality may be a localized variation in surface grating pitch. The image viewing axis may be substantially coincident with the primary viewing axis.

[0014] The optical center of the spectacle lens may be offset relative to the main gaze axis. The optical center of the spectacle lens may be offset relative to the main gaze axis, and the vertex of the holographic optical element may be offset relative to the optical center of the spectacle lens.

[0015] The optical center of the lens can be offset between 0 and 40 degrees, preferably between 5 and 10 degrees, relative to the main viewing axis, and the vertex of the holographic optical element (and therefore the image viewing axis) can be offset between 0 and 40 degrees, preferably between 5 and 10 degrees, relative to the optical center of the lens.

[0016] The holographic optical element may include a second variation of the holographic function to compensate for a shift of the optical center of the lens relative to the primary viewing axis and to compensate for a shift of the vertex of the holographic optical element relative to the optical center of the lens. The second variation of the holographic function may be a localized variation of the surface grating pitch. The first and second variations of the holographic function may be variations in the phase gradient.

[0017] According to a second aspect, a wearable head-up display is provided, comprising: a spectacle lens according to the first aspect; a spectacle frame; and an image source, wherein the spectacle lens is mounted in the frame and the image source is mounted on an arm of the frame adjacent to the spectacle lens to project light onto a holographic optical element of the spectacle lens, thereby generating one or more image eyepoints.

[0018] One or more eyepoints may be generated symmetrically about the gaze axis. Alternatively, one or more image eyepoints may be generated asymmetrically about the gaze axis.

[0019] The angle of the chief ray from the image source relative to the holographic optical element can be constant. The vertex of the holographic optical element can be aligned relative to the chief ray of the image source such that the chief ray coincides with the vertex. The holographic optical element can be offset relative to the point where the chief ray intersects the plane of the holographic optical element in air to account for refraction caused by the eyeglass lens.

[0020] The image viewing axis can be offset from the primary gaze axis in the horizontal plane by an amount equal to the wrap angle of the spectacle lens mounted in the spectacle frame. The image viewing axis can be offset from the primary gaze axis in the vertical plane by an amount equal to the forward tilt angle of the spectacle lens mounted in the spectacle frame.

[0021] The first change of the hologram function is a change of the phase of the hologram function to compensate for the wrap angle and the front tilt angle of the holographic optical element.

[0022] The eyeglass lens may include a first lens portion formed on a second lens portion with an interface therebetween; and a holographic optical element interposed between the first and second lens portions at the interface.

[0023] The interface can be a curved interface. The curved interface can be cylindrical. The spectacle lens can have a major axis and a minor axis. The cylindrical interface can have a curved profile in the direction of the major axis and a straight profile in the direction of the minor axis. Alternatively, the curved interface can be spherical. The curved interface surface can contribute both vertical and horizontal diopters, and the holographic optical element can be configured and arranged to compensate for both vertical and horizontal diopters.

[0024] Arrangements according to the present disclosure solve one or more of the above-mentioned 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 eyeglass lens and combining the HOE position with the gaze direction, i.e., for different recommended gaze positions, the digital image content directed at the user's eye will have minimal variation that may otherwise be caused by variations in the HOE to user pupil distance, IPD, wrap angle and tilt angle, or other physiological factors related to the eyeglass and frame design. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order that the manner in which the features of the present disclosure may be understood in detail, a more particular description will be given with reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the drawings illustrate only typical embodiments and are not to be considered limiting of their scope. The figures are provided to facilitate understanding of the present disclosure and are not necessarily drawn to scale. The 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 which like reference numerals are used to designate like elements, and in which:

[0026] Figure 1a shows a front view of an eyeglass lens for a wearable head-up display (HUD) according to an embodiment;

[0027] Figure 1b Shown Figure 1a A side view of a spectacle lens;

[0028] Figure 2a An eyeglass lens comprising a holographic optical element having a plurality of eye points arranged symmetrically about a gaze direction is shown;

[0029] Figure 2b Shown Figure 2a The wrap angle of the eyeglass lens relative to the user's eye direction;

[0030] Figure 3 An eyeglass lens comprising a holographic optical element having a plurality of eyepoints asymmetrically arranged about a gaze direction is shown;

[0031] Figure 4a Shown Figure 1a and 1b The forward tilt angle of the eyeglass lens relative to the user's pupil;

[0032] Figure 4b Shown Figure 4a a close-up view of the eyeglass lenses shown;

[0033] Figure 4c Shown Figure 1a and1b A side view of the eyeglass lens relative to the user's pupil;

[0034] Figure 5a Shown Figure 1a and 1b Cross-section of a spectacle lens;

[0035] Figure 5b yes Figure 5a Exploded view of area A in the middle;

[0036] Figure 6a shows a perspective view of a spectacle lens according to an embodiment;

[0037] Figure 6b Shown Figure 6a a cross-section of a spectacle lens; and

[0038] Figure 7a shows an exploded perspective view of an eyeglass lens assembly according to an embodiment;

[0039] Figure 7b shows a perspective view of an eyeglass lens assembly according to an embodiment;

[0040] Figure 8 shows the laminated structure of the front and back lens parts with a holographic optical element stack consisting of multiple holographic layers in between; and

[0041] Figure 9 An AR system in the form of AR glasses including glasses lenses according to the embodiment is shown. DETAILED DESCRIPTION

[0042] Before describing the embodiments of the present disclosure, it is necessary to define some common optometric terms used in this specification.

[0043] The term primary gaze axis / direction is defined as the user's gaze looking straight ahead at a point on the horizon at infinity. The position of the lens' optical center relative to the primary gaze direction can affect a user's visual acuity and eye alignment while wearing the glasses.

[0044] The term pantoscopic tilt (or simply "tilt") is defined as the angle in the 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 person's corneal plane, an imaginary plane passing through the center of the user's eye. A pantoscopic tilt that is too steep may cause eye fatigue and discomfort to the user, while a pantoscopic tilt that is too shallow may cause the frame to slide down the bridge of the nose and interfere with vision. In AR applications, the pantoscopic tilt angle may be between 0 and 20 degrees, depending on the design of the frame.

[0045] The term frame wrap (or simply wrap) is an angle that describes the horizontal angle of the lens plane relative to the primary gaze axis / 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 may affect the amount of peripheral vision provided by the lens. A higher wrap angle can provide more peripheral vision coverage, which can be beneficial for certain activities such as sports or driving. However, a higher wrap angle may also cause the lens to be larger and more obstructive, which may not be ideal for all users. In AR applications, the wrap angle may be between 0 and 20 degrees, depending on the design of the frame.

[0046] The term interpupillary distance (IPD) is the distance between the centers of the pupils of the two eyes measured in millimeters. IPD varies from 42mm to 75mm among people.

[0047] The term "eyeglass plane" is defined by the wrap angle and tilt angle of the frame design. The optical axis is perpendicular to the eyeglass plane and passes through the optical center of the eyeglass lens. In this context, the optical center of a lens is the point through which light rays pass through the lens without being deflected. In concave corrective lenses, this is usually the thinnest part of the lens.

[0048] The term eye relief (also called back vertex distance or BVD) refers to the distance along the primary gaze axis from the pupil to the eyeglass plane. In the discussion of the following embodiments, the eyeglass plane is identical to the plane of the holographic optical element integrated into the eyeglass lens.

[0049] The term gaze offset refers to the angular offset from the primary gaze axis at which the displayed content is viewed. Those skilled in the art will appreciate that the gaze offset may be zero, in which case it will substantially coincide with the primary gaze direction. More generally, when the angle between two axes is given as zero, those skilled in the art will appreciate that this means the axes, or points on the axes, coincide.

[0050] Figure 1a and 1b A front view and a top cross-sectional view are shown, respectively, of an eyeglass lens 100 according to an embodiment, which integrates a holographic optical element (HOE) 102 and is suitable for use in a wearable head-up display (HUD). The eyeglass lens 100 can be of any suitable shape, where the shape is largely determined by the design and contours of the eyeglass frame to which the eyeglass lens 100 is to be mounted (see, for example, FIG. Figure 9Suitable shapes for eyeglass lenses 100 incorporating a holographic optical element (HOE) 102 are manufactured from prefabricated lens blanks or "pucks," as discussed in more detail below.

[0051] Spectacle lens 100 includes an optical center 104 and a geometric center 106. The optical center of a lens is the point where the lens material-air interface is parallel, allowing light to pass through the lens without deflection. This is the thinnest portion 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 of the lens coincides with the optical center 104 of the lens depends on the shape of the lens in the frame, that is, how the lens is formed from the lens blank to fit the frame (called glazing). This is typically a design choice based on the wrap angle and tilt angle, as well as the content direction (the direction the image is viewed).

[0052] When mounted in an eyeglass frame, the optical center 104 of the eyeglass lens may approximately coincide with the pupil of the user's eye based on the user's IPD. This is particularly important when the eyeglass lens has a corrective optical power to correct the user's prescription. Therefore, depending on the specific user's IPD and how the eyeglass lens 100 was cut from the lens blank, the optical center 104 may not coincide with the geometric center 104 of the eyeglass lens 100. In the case of zero-prescription lenses for AR applications, the user's IPD will determine the optimal position of the HOE.

[0053] The primary gaze direction (or axis) is defined as the axis PP from the user's eye through the eyeglass lens 100 while the user is looking straight ahead and toward the distant horizon in an untilted orientation of the head. The HOE 102 also includes a geometric center and a vertex, where the geometric center and the vertex may or may not coincide. The vertex of the HOE is defined by a reference pixel corresponding to the center pixel at which the virtual or digital image content can be viewed and is the point at which the principal ray from the image source impinges on the HOE. The vertex can also be defined relative to a reference pixel of the projected image around which all other pixels are calibrated. Based on the known position of the holographic optical element, the vertex is positioned to achieve the image viewing axis.

[0054] The vertex of the HOE 102 is substantially aligned with or coincides with the gaze offset direction (also referred to as the image viewing axis II). For augmented reality applications, it may be desirable to offset the digital image content from the primary gaze direction PP so that the display of the digital content does not interfere with the user's view of the world along the primary gaze direction. In this case, the vertex of the HOE 102 is offset from the primary gaze axis of the eyeglass lens 100 so that the digital content is not visible when the user looks through the eyeglass lens along 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, and thus the digital image content is offset from the primary gaze axis PP by an angular offset, referred to as the gaze offset θ. GO ,like Figure 1b As shown. Those skilled in the art will understand that Figure 1b While a horizontal gaze offset is shown, a vertical angle is also possible. The gaze offset axis can be defined by horizontal and / or vertical angles relative to the primary gaze direction. The gaze offset can be defined by polar and azimuthal coordinates relative to the primary gaze axis and a tangent plane to the lens surface perpendicular to the primary gaze axis. The gaze offset can be defined at the maximum horizontal rotation (maximum condition) of the user's eye relative to the primary gaze axis (minimum condition). Therefore, the gaze offset is the angular offset from the primary gaze axis at which digital content is visible and may intersect the HOE 102 at a different point from 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, when the user looks through the eyeglass lens 100, the digital content can be viewed in the primary gaze direction. Therefore, the maximum limit on the gaze offset direction is defined by the maximum rotation of the user's eye from the primary gaze position, which, based on a human eyeball of approximately 25 mm, can be approximately ±40 degrees horizontally (adduction or abduction), 28 degrees for looking upward, and 47 degrees for looking downward. Those skilled in the art will appreciate that maintaining eye rotation to its maximum limit for extended periods may be uncomfortable for some users. Therefore, the horizontal and vertical image viewing angles are preferably no more than about 12 degrees, and more preferably between about 4 degrees and 11 degrees, wherein the lower limit of 4 degrees ensures that digital image content is not placed in the primary gaze direction, which could be distracting to the user.

[0055] The multiple eye points (or eye boxes) can be arranged in a spaced pattern, such as a grid pattern, a linear array, an nxm array (where n and m are positive integers). The multiple eye points can be arranged symmetrically around the gaze axis II, such as Figure 2a and 2b As shown in the figure, which will be discussed in more detail below (the so-called symmetry condition). Alternatively, multiple eye points can be arranged asymmetrically around the gaze axis, such as Figure 3As shown, this will be discussed in more detail below (the so-called asymmetric condition). Alternatively, the single eyepoint defining the entire eyebox may be arranged to coincide with or offset from the gaze axis II.

[0056] As mentioned above, Figure 2a and 2b According to an embodiment, a symmetrical arrangement of multiple eye points 108 is shown. Figure 2a As shown, each eye point 108 is symmetrically arranged around the vertex of the HOE 102, and the geometric center of the HOE substantially coincides with the optical center 104 of the spectacle lens 100. The geometric center 106 of the lens is also shown. The multiple eye points 108 can be symmetrically arranged around the optical center 104 of the spectacle lens 100, and since the optical center of the spectacle lens coincides with the gaze deviation direction, the multiple eye points will be symmetrically arranged around the axis II ( Figure 2b Reference numeral 112). Although Figure 2a While four eyepoints 108 are shown, those skilled in the art will appreciate that any number of eyepoints 108 may be used, as long as they are symmetrically arranged. Those skilled in the art will also appreciate that eyepoints 108 may be spaced to define an effective replica eyebox area within which a user may view digital image content.

[0057] Figure 2b is a top view showing the lens wrap angle, showing Figures 1a to 2b The eyeglass lens 100 and HOE 102 are positioned relative to the user's eye. The primary gaze axis PP is represented by axis 110, which runs from the eye pupil to the vertex of the HOE 102. The gaze offset direction 112 is represented by axis II. As an 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 is incident on the vertex of the holographic optical element 102. The chief ray from the image source 116 is incident on 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 at the HOE vertex may be 56 degrees relative to the normal to the HOE surface. Typical wrap angles for eyeglass lenses may be between 0 and 20 degrees. The beamlets 118, 118' are deflected from the projection beam 114 by the holographic optical element 102, pass through the user's pupil, and reach the retina of the eye, forming an eyepoint 108 collimated at the user's pupil.

[0058] like Figure 3 As shown, each eye point 108 is asymmetrically arranged around the vertex (and axis II) of the HOE 102. Thus, the plurality of eye points 108 are asymmetrically arranged around the gaze direction. Figure 3While four eyepoints 108 are shown, those skilled in the art will appreciate that any number of eyepoints 108 may be used, provided they are arranged asymmetrically. As with the symmetrical arrangement described above, those skilled in the art will also appreciate that the eyepoints 108 can be spaced to define an effective replicated eyebox area within which the user can view digital image content. As an example, the gaze offset direction can be any angle dependent on the maximum comfortable rotation of the user's eyes. The projection beam 114 from the image source 116 is incident on the holographic optical element 102 as described above.

[0059] exist Figure 4a and 4b , the concept of the tilt angle of the eyeglass lens 100 is shown according to an embodiment, with the main gaze direction represented by axis 402 and the gaze offset direction represented by axis 404. The tilt angle is the angle θtilt between the main gaze axis 402 and the normal from the center of the pupil to the back surface of the eyeglass lens. Changes in this distance, also known as the back vertex distance (BVD), can change the field of view (FOV) or the size of the viewable digital image content. Large changes in the BVD may result in image clipping, image offset, or reduced image brightness. Here, the BVD is the distance from the center of the pupil to the center of the holographic optical element 104. The gaze offset axis is arranged to coincide with the tilt angle. By positioning the position of the vertex of the holographic optical element 102 relative to the gaze offset direction 112, changes in the position of the beamlets on the retina caused by slight changes in the distance from the holographic optical element 102 to the pupil of the user's eye will be minimized. For a given HOE area, the BVD is inversely proportional to the FOV.

[0060] exist Figure 4c 4 , the wrap angle of the spectacle lens 100 is shown according to an embodiment. The primary gaze direction is represented by axis 402, the gaze offset direction is represented by axis 404, and the wrap angle is the angle θwrap between the primary gaze axis 402 and the wrap angle. Like the tilt angle θtilt, 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 vertex of the holographic optical element 102. The arrangement of the tilt angle and the wrap angle is further illustrated in FIG. 4 d. The optical center of the spectacle lens 100 coincides with the wrap angle and tilt offset point 406. Typical tilt angles for spectacle lenses may range from 0 to 20 degrees.

[0061] The image viewing axis deviates from the main gaze axis in the horizontal plane by a horizontal image viewing angle and in the vertical plane by a vertical image viewing angle. The horizontal image viewing angle and the vertical image viewing angle are limited by the maximum rotation of the eye. In this case, the holographic optical element can include a first variation of the holographic function, configured and arranged to compensate for the horizontal and vertical image viewing angles that deviate from the main gaze axis. The first variation of the holographic function is formed by a local variation of the surface grating spacing when recording the holographic function. The variation of the surface grating spacing can be a variation of the local phase gradient. Similarly, the variation of the holographic function can also be achieved by a variation of the volume of the HOE holographic material or the internal fringe spacing.

[0062] The optical center 104 of the spectacle lens 100 can be offset relative to the main gaze axis PP, and the vertex of the holographic optical element 102 and the image viewing axis are offset relative to the optical center 104 of the spectacle lens 100. The optical center of the spectacle lens 100 is offset between 0 and 20 degrees relative to the main gaze axis, preferably between 4 and 11 degrees, and the vertex of the holographic optical element is offset between 0 and 20 degrees relative to the optical center of the lens, preferably between 4 and 11 degrees.

[0063] The holographic optical element 102 can include a second variation of the hologram function to compensate for a shift of the optical center 104 of the spectacle lens 100 relative to the principal gaze axis and for a shift 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 hologram function is achieved by a local variation of the surface grating pitch when recording the hologram function. The further variation of the surface grating pitch can be achieved by changing the phase of the local grating gradient. The further variation takes into account the shape of the world-side and eye-side surfaces of the spectacle lens.

[0064] The image viewing axis is offset in the horizontal plane from the primary gaze axis by an amount equal to the wrap angle of the spectacle lens mounted in the spectacle frame (hereinafter referred to as Figure 9 (Discussion). Similarly, the image viewing axis is offset from the primary gaze axis in the vertical plane by an amount equal to the forward tilt angle of the spectacle lens 100 mounted in the spectacle frame. Therefore, one skilled in the art will appreciate that the first change in the hologram function is a change in the phase of the hologram function to compensate for the wrap angle and forward tilt angle of the holographic optical element integrated with the spectacle lens 100 mounted in the spectacle frame.

[0065] When the holographic optical element 102 is embedded in the eyeglass lens 100, as shown in FIG. Figure 5a As shown, the angle of the beam 114 from the projector 116 needs to be aligned to compensate for the refractive index and thickness of the material of the eyeglass lens 100. Based on the projector beam angle θ Proj, i.e., the angle between the projector beam and the local surface normal 120 at the point of incidence of the beam on the spectacle lens 100, the beam impinging on the spectacle lens at the ocular-side surface 122, the refractive index of the spectacle lens material being 1.5, and the thickness of the lens material being 1.6 mm, the position X between the nominal facing position and the point of incidence of the chief ray (projector beam 114) from the projector 116 on the ocular-side surface of the spectacle lens needs to be adjusted. More generally, based on the foregoing, one skilled in the art will appreciate that it is not possible to align the vertex of the holographic optical element 102 at the center of rotation such that the beam 114 from the projector 116 hits the vertex. Figure 5b yes Figure 5a Exploded view of region A in FIG. The holographic optical element includes an optical function to compensate for the curvature of the lens surface when the light beam 114 from the projector 116 is incident on the lens and to compensate for the refractive index of the lens material. This optical function takes into account the incident angle θ due to 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.

[0066] For the above-mentioned refractive index of 1.5 and thickness of 1.6 mm, if the refraction of the light beam 114 from the projector 116 is not taken into account, a displacement X of up to 1.07 mm relative to the unrefracted light beam 114 may occur.

[0067] The eyeglass lens according to the embodiment may embed the holographic optical element into the eyeglass lens material by any appropriate process. For example, Figure 6a A holographic optical element (not shown for clarity) is shown encapsulated in an eyeglass lens 100 by forming the eyeglass lens from two components, wherein the interface between the two parts is a cylindrical profile. The holographic optical element may be formed from a thin film material, such as a photopolymer or silver halide. The parameters of thin films are generally well understood, but in this context the thickness of the film (e.g. a photopolymer film or a silver halide film) may be of the order of 100 microns or less. It is typically a low absorption, optically clear (or transparent) low haze film suitable for integration into a lens without significantly affecting the perspective. The reference plane 202 of the eyeglass lens in the center of the xz plane is highlighted here. See also Figure 6b , which shows Figure 6a Cross-section of a spectacle lens at a reference plane 202. Here, the cylindrical interface outline 203 between the two component parts is shown as a dashed line.

[0068] The two component parts are typically manufactured separately, but can alternatively be formed from split eyeglass lenses. Cylindrical surfaces on a lens or lens component are not typical. A cylindrical surface between two lens components can be made by grinding or custom molds (injection molding). Alternatively, 3D printing can be used to make the lens components. Manufacturing lens components with cylindrical interfaces is not a standard technique. However, it is possible using injection molding (e.g. plastic), grinding or 3D printing. Standard lens grinding and mold manufacturing may use diamond turning, which generally means spherical surfaces, but this and other techniques can be used to achieve cylindrical surfaces.

[0069] Next reference Figure 7a , depicting Figure 6a Component parts of an eyeglass lens. These include: a first component part (including the eye-facing surface) 701; and a second component part (including the world-facing surface) 702. The interface between the first component part 701 and the second component part 702 has a cylindrical shape (e.g. Figure 6b ), is curved in the xz plane (in this case, a circular arc segment) and flat in the yz plane (and also flat in the xy plane). A holographic optical element with the same dimensions as the glasses in the x and y dimensions and the same profile ( Figure 7a The holographic optical element (not shown) is laminated at the cylindrical interface between the first component part 701 and the second component part 702. When the first component part 701 and the second component part 702 are then connected to each other, the holographic optical element is completely encapsulated within the eyeglass lens. Lamination on a cylindrical surface avoids the deformation associated with lamination on a spherical surface. The interface is preferably perfectly cylindrical, but can be a partial spherical cylinder or a toric, as long as any deviation from a pure cylindrical shape is negligible at the HOE location. The closer the interface is to a perfect cylinder, the lower the stress in the film.

[0070] As described above, the cylindrical interface between the first component part 701 and the second component part 702 is flat along one axis. Therefore, it exhibits the same geometric limitations along this axis as using a planar film. However, since eyeglass lenses typically have a significant aspect ratio, this limitation becomes less significant if it applies only to the shorter (minor) axis of the eyeglass lens, as discussed further below. The film can be attached to the cylindrical surface of one of the lens components in a variety of ways. Lamination of the film may not require the film to adhere to one or both surfaces of the cylindrical interface (the first component part 701 and the second component part 702 can simply be attached to each other with the film sandwiched between them), but additional adhesion can be provided. The HOE can be a photopolymer, such as Bayfol (RTM) HX (sold by Covestro AG), typically having a substrate thickness of approximately 60 microns and a polymer layer thickness of approximately 20 microns. The photopolymer is then typically provided with an adhesive film on one side, which adheres to the glass or plastic once laminated to the surface using a roller (or similar tool). Alternatively or additionally, glue, double-sided tape, vacuum treatment, heat treatment, or pressure treatment may be used to adhere the HOE to the substrate. The HOE may also be a silver halide film, and the above techniques may also be used to adhere the film to the substrate surface. The choice of lens material may aid adhesion; for example, polycarbonate may provide better adhesion. The film typically does not extend completely to the edge of the cylindrical interface. This may allow for better encapsulation (no moisture infiltration) if a good glue seal is applied all the way around.

[0071] refer to Figure 7b , schematically showing the Figure 7a 1. Spectacle lens 100 assembled from component parts. Also shown is a film 104 encapsulated between a first component part 701 and a second component part 702. Thus, a finished spectacle lens 703 is created by fitting the two component parts together via a cylindrical interface, with the film 704 sandwiched between them.

[0072] The eye-facing component (first component portion 701) can be molded into the desired shape of the spectacle lens. More typically, it is molded as a lens blank, where the component has a cylindrical profile on the front surface (bonded to the world-facing component 702), but the back surface may be flat or have some arbitrary surface curvature. The first component portion 701, the second component portion 702, and the film 104 are then bonded to form the lens "blank" spectacle lens 100 with the HOE embedded.

[0073] Once the assembled eyeglass lens 100 is formed in this manner, it will present a rounded profile lens blank, the back surface of which can be ground like a standard lens blank to produce the final lens. In order to fit the eyeglasses, the front and back curvatures are typically trimmed (edge ground) to fit the eyeglass frame. This treatment can be performed on the first component part 701 and the second component part 702 before film packaging and assembly, or after assembly. The grinding process, i.e., the front surface and / or the back surface are ground to a curvature, is a more intensive process than trimming, and if necessary, it is preferably performed on the first component part 701 and / or the second component part 702 before film packaging and assembly.

[0074] Therefore, the world-facing component is typically formed to include a front surface (usually a spherical surface with the desired base curvature) and a back surface with a cylindrical profile. The eye-facing component can be formed to include a front surface with a cylindrical profile and a back surface. The back surface can be formed to have the curvature required for the final prescription. Alternatively, the back surface can remain flat (or have an arbitrary curvature) to create a lens blank, so that further grinding of this surface will be used to set the prescription.

[0075] The holographic optical element can be configured to act as a plane mirror. In this case, the holographic optical element itself may not add any optical power. 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 compounded. The optical power that the eyeglass lens presents to the real world is determined solely by the curvature of the inner and outer surfaces of the eyeglass lens. Alternatively, the eyeglass lens can be configured so 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 generated by the curvature of the cylindrical interface. The HOE can then act as a reflective power optical element (which is typical in AR applications). The holographic optical element can be a photosensitive material, and the hologram can be recorded on the photosensitive material to form the holographic optical element. In some cases, recording the hologram on the photosensitive material may include: providing the photosensitive material on a planar substrate; and recording the hologram on the photosensitive material when on the planar substrate, recording the hologram to compensate for the optical power of the cylindrical interface. This can thereby provide a holographic optical element, which can then be applied to the cylindrical interface. In other cases, recording a hologram on a photosensitive material may include: applying the photosensitive material to a cylindrical interface; and recording the hologram on the photosensitive material while on the cylindrical interface. In other cases, a projector or image source other than a hologram may be compensated.

[0076] When it comes to compensating for optical power, the rear surface of the spectacle lens, or in other words, the surface facing the eye, is most critical to the function of the holographic optical element. The effective curvature of the rear surface of the spectacle lens consists of optical power components in the horizontal and vertical planes, with the power in these planes differing. 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 on the eye-facing side of the spectacle lens, and the back center thickness. To avoid astigmatism caused by the eyepoint being too far or too close to the holographic optical element, it is necessary to record a holographic function 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 might contribute -4D in the vertical direction and +8.9D in the horizontal direction.

[0077] A spectacle lens according to an embodiment may comprise a holographic optical element 102 comprising a holographic layer stack HOL1, HOL2 between two lens parts, such as Figure 8 As shown. Hologram layer stack HOL1, HOL2 includes multiple hologram layers. Figure 8 While two hologram layers HOL1 and HOL2 are shown, those skilled in the art will appreciate that any number of hologram layers HOL1 and HOL2 may be included, depending on the specific application. For example, one or more hologram layers may be visible wavelength holograms. One or more hologram layers may be infrared (IR) wavelength holograms. IR holograms may be used when eye tracking is required in an AR system.

[0078] When a holographic optical element is composed of multiple holographic layers, it is necessary to align the holograms with each other and with the eyeglass lens. This process is called registration. To achieve this, those skilled in the art will appreciate that a system of registration marks or fiducials can be used to align adjacent holographic layers with each other and, according to the above-described embodiments, with the eyeglass lens.

[0079] As described above, the spectacle lens 100 can be of any suitable shape, where the shape is largely determined by the design and contours of the spectacle frame in which the spectacle lens 100 will be mounted. The desired shape of the spectacle lens 100 with the integrated HOE 102 can be cut or milled from a lens blank or "wafer." Alternatively, the spectacle lens or portion of the spectacle lens can be manufactured by injection molding and / or overmolding.

[0080] Figure 9An augmented reality system is shown, comprising at least one eyeglass lens as described above. The augmented reality system takes the form of a wearable head-up display, such as a pair of glasses 900. Like known types of glasses, the glasses 900 according to an embodiment include a frame 902. The frame includes arms 904 and lens mounting portions 906 connected by a nose bridge portion 908. One of the arms 904 includes a mounting portion 910 in which a projector (as described above) is fixedly mounted, such that a beam 114 ( Figure 9 (not shown) will strike the spectacle lens 100 according to the above-described embodiment. Those skilled in the art will appreciate that the projector 116 will be mounted on the arm 904 adjacent to the lens mounting portion 906 that houses the spectacle lens 100 according to the embodiment. Another lens mounting portion can accommodate a standard ophthalmic lens. Alternatively, the spectacle lens according to the embodiment can be mounted in another lens mounting portion, and an additional projector system 116 may be mounted on the corresponding mounting portion on the arm 904.

[0081] One or both of the mirror arms 904 may also be adapted to accommodate a battery (not shown) to power the projector described above. In addition, one or both of the mirror arms 904 may also 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. In addition, the operation of the projector may be controlled by control electronics, an eye tracking system (not shown). The eye tracking system may include a non-visible light source, such as an infrared LED, directed toward the user's eye, and a light sensor arranged to capture the non-visible light reflected by the user's eye. The embodiments described herein are equally applicable to waveguide-based or free-space AR systems.

[0082] Particular and preferred aspects of the present disclosure are set out in the accompanying independent claims. Combinations of features from the dependent claims and / or independent claims may be combined as appropriate and not just in the combinations set out in the claims.

[0083] The scope of the present disclosure includes any novel feature or combination of features disclosed therein, whether explicitly or implicitly, or any generalization thereof, whether or not related to the claimed disclosure or alleviating any or all of the problems addressed by the present disclosure. The applicants hereby give notice that new claims may be formulated to such features during the prosecution of this application or of any further application derived therefrom. In particular, with reference to the appended claims, features of dependent claims may be combined with features of the independent claims, and features of the independent claims may be combined in any appropriate manner, and not merely in the specific combinations recited in the claims.

[0084] 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 comprising: Optical center, main viewing axis and holographic optical element with vertex, wherein the holographic optical element is integrated with an eyeglass lens such that the vertex coincides with an image viewing axis to allow viewing of digital content, and wherein the optical center of the lens is positioned relative to the primary gaze axis and the vertex is positioned relative to the optical center.

2. The spectacle lens according to claim 1, wherein the image viewing axis is offset from the main gaze axis.

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

4. The spectacle lens according to claim 3, wherein the horizontal image viewing angle is between 0 degrees and 40 degrees in the adduction or abduction direction, preferably between 4 degrees and 12 degrees; the vertical image viewing angle is between 0 degrees and 28 degrees in the upward direction and between 47 degrees in the downward direction, preferably between 4 degrees and 12 degrees.

5. The eyeglass lens of claim 1 , wherein the holographic optical element comprises a first variation of the hologram functionality configured and arranged to compensate for horizontal and vertical image viewing angles that deviate from a primary gaze axis.

6. The eyeglass lens according to claim 5, wherein the first variation of the hologram function is a local variation of the grating pitch and / or the fringe pitch of the inner surface of the holographic material of the holographic optical element.

7. The spectacle lens according to claim 1, wherein the image viewing axis is substantially coincident with the primary gaze axis.

8. The spectacle lens of claim 1 , wherein the optical center of the lens is offset relative to the primary gaze axis.

9. The spectacle lens according to claim 1, wherein the optical center of the spectacle lens is offset relative to the main gaze axis, and the vertex of the holographic optical element is offset relative to the optical center of the spectacle lens.

10. A spectacle lens according to any preceding claim, wherein the optical centre of the lens is offset by between 0 and 20 degrees, preferably between 5 and 10 degrees, relative to the main gaze axis, and the vertex of the holographic optical element is offset by between 0 and 20 degrees, preferably between 5 and 10 degrees, relative to the optical centre of the lens.

11. The eyeglass lens according to claim 1 , wherein the holographic optical element comprises a second variation of the hologram function to compensate for a shift of the optical center of the lens relative to the main gaze axis and to compensate for a shift of the vertex of the holographic optical element relative to the optical center of the lens.

12. The eyeglass lens of claim 11, wherein the second variation of the holographic functionality is a local variation of the surface grating pitch.

13. Spectacle lens according to claims 6 and 11, wherein the first and second variations of the hologram function are variations of the phase gradient.

14. A wearable head-up display comprising: The spectacle lens according to claims 1 to 13; Eyeglass frames; and image sources, The eyeglass lens is mounted in a frame, and the image source is mounted on an arm 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 eye points. The wearable head-up display according to claim 14 , wherein the one or more eye points are generated symmetrically around a gaze axis.

16. The wearable head-up display of claim 14, wherein the one or more image eyepoints are generated asymmetrically around a gaze axis.

17. A wearable head-up display according to claims 14 to 16, wherein the chief ray angle from the image source relative to the holographic optical element is constant.

18. A wearable head-up display according to claims 14 to 17, wherein the vertex of the holographic optical element can be aligned relative to a chief ray of an image source such that the chief ray coincides with the vertex.

19. A wearable head-up display according to claims 14 to 18, wherein the holographic optical element can be offset relative to the intersection of the chief ray in air with the plane of the holographic optical element to account for refraction due to eyeglass lenses.

20. A wearable head-up display according to claims 14 to 19, wherein the image viewing axis is offset from the primary gaze axis in the horizontal plane by an amount equal to the wrap angle of an eyeglass lens mounted in an eyeglass frame.

21. A wearable head-up display according to claims 14 to 20, wherein the image viewing axis is offset from the primary gaze axis in the vertical plane by an amount equal to the forward tilt angle of eyeglass lenses mounted in an eyeglass frame.

22. The wearable head-up display according to claims 14 to 21, wherein the first change of the hologram function is a change of the phase of the hologram function to compensate for the wrap angle and the forward tilt angle of the holographic optical element.

23. The spectacle lens according to claims 1 to 13, wherein the spectacle lens comprises a first lens portion formed on a second lens portion with an interface therebetween; and the holographic optical element is interposed between the first and second lens portions at the interface.

24. The spectacle lens according to claim 23, wherein 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 has a curved profile in the direction of the major axis and a straight profile in the direction of the minor axis.

25. The spectacle lens of claim 24, wherein the curved interface surface contributes vertical and horizontal diopters to the spectacle lens, and wherein the holographic optical element is configured and arranged to compensate for the vertical and horizontal diopters of the lens.

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