CLAIM OF PRIORITY

[0001] This application claims priority to U.S. Provisional Patent Application No. 63/500,441 , entitled “Varifocal Eyeglasses”, filed May 5, 2023, which is incorporated by reference herein in its entirety.

FIELD

[0002] The following is related generally to the field of viewing devices and, more specifically, to eyeglasses for immersive displays or vision correction.

BACKGROUND

[0003] Varifocal technologies are of great importance for immersive viewing devices. Varying focal lengths is disruptive to vision perspectives and cause motion sickness. Thin lens, such as used in such eyeglasses and many immersive viewing systems, have poor off-axis image quality and can cause “tunnel vision” for both immersive 3D displays and eyeglasses for presbyopia (i.e., age-related farsightedness). Consequently, there would be a great advantage to a varifocal system that is ultimately realistic to our human natural vision.

SUMMARY

[0004] According to one aspect of the present disclosure, an eyeglass system includes: a first lens; a frame configured to place the first lens at a first distance in front of a first eye of a user; a measuring device coupled to the frame and configured to measure a distance between the first lens and the first eye of the user; and a controller. The controller is configured to: determine by use of the measuring device of the distance between the first lens and the first eye of the user.

[0005] Optionally, in the preceding aspect, the frame includes one or more actuators configured to move the first lens in at least one of a plurality of direction, and where controller is further configured to adjust the first distance based on the determined distance between the first lens and the first eye of the user by generating control signals to the one or more actuators to prompt the actuator to move the first lens in the at least one of the plurality of directions.

[0006] Optionally, in any of the preceding aspects, the controller is further configured to determine by use of the measuring device of the distance between the first lens and the first eye of the user.

[0007] Optionally, in the preceding aspect, the controller is further configured to adjust the first distance to correspond to a focal length of the first eye.

[0008] Optionally, in any of the preceding aspects, the first distance is manually adjustable by the user.

[0009] Optionally, in the preceding aspect, the controller is further configured to provide feedback to the user in response to manually adjusting the first distance.

[0010] Optionally, in any of the preceding aspects, the first lens is a negative focal length lens configured of presbyopes assistance.

[0011] Optionally, in any of the preceding aspects, the eyeglass system is an immersive display system further comprising an immersive display, the first lens located between the immersive display and the first eye.

[0012] Optionally, in the preceding aspect, the controller is further configured to render images for presentation on the immersive display.

[0013] Optionally, in the preceding aspect, to render the images for presentation on the immersive display, the controller is further configured to incorporate the first distance into algorithms to render the images. [0014] Optionally, in any of the preceding aspects, the frame is further configured to place the first lens at the first distance in front of a second eye of the user.

[0015] Optionally, in any of the preceding aspects, the eyeglass system further comprises: a second lens, wherein the frame is further configured to place the second lens at a second distance in front of a second eye of a user, herein the one or more actuators are further configured to move the second lens in at least one of a plurality of direction independently of the first lens, and wherein the measuring device is further configured to measure a distance between the second lens and the second eye of the user. The controller is further configured to: determine by use of the measuring device of the distance between the second lens and the second eye of the user; and adjust the second distance based on the determined distance between the second lens and the second eye of the user by generating control signals to the one or more actuators to prompt the actuator to move the second lens in the at least one of the plurality of directions.

[0016] Optionally, in any of the preceding aspects, the measuring device is further configured to determine a gaze of the user, and the controller is further configured to adjust a focal length of the first lens in response to the determined gaze.

[0017] Optionally, in the preceding aspect, the first lens comprises a liquid crystal layer and the controller is further configured to adjust the focal length of the first lens by adjusting a refractive index of the liquid crystal layer.

[0018] Optionally, in any of the preceding aspects, the controller is further configured to adjust the focal length of the first lens by adjusting a curvature of a surface of the first lens.

[0019] Optionally, in any of the preceding aspects, subsequent to adjusting the first distance, the controller is further configured to: re-determine by use of the measuring device of the distance between the first lens and the first eye of the user; and update the adjustment of the first distance based on the determined distance between the first lens and the first eye of the user.

[0020] Optionally, in any of the preceding aspects, the measuring device configured to measure the distance between the first lens and the first eye of the user comprises a MEMS (micro-electromechanical system) based Lidar (light detection and ranging) sensor.

[0021] According to an additional aspect of the present disclosure, there is provided a method of determining, by a measuring device coupled to a frame of an eyeglass system configured to place a first lens in front of a first eye of a user, a distance between the first lens and the first eye of a user wearing the eyeglass system; determining by the measuring device of a focal length of the first eye of the user wearing the eyeglass system; and adjusting by a controller of the eyeglass system of the distance to correspond to the focal length of the first eye.

[0022] Optionally, the preceding aspect, the method further comprises: determining by the measuring device a gaze of the user wearing the eyeglass system; and adjusting a focal length of the first lens in response to the determined gaze.

[0023] Optionally, the preceding aspect, the first lens comprises a liquid crystal layer and the method further comprises adjusting the focal length of the first lens by adjusting a refractive index of the liquid crystal layer.

[0024] According to a further aspect, an immersive display includes: a first lens; a frame configured to place the first lens at a first distance in front of a first eye of a user, the frame including one or more actuators configured to move the first lens in at least one of a plurality of direction; an immersive display, the first lens located between the immersive display and the first eye; a measuring device a measuring device coupled to the frame, the measuring device configured to measure a distance between the first lens and the first eye of the user; and a controller configured. The controller is configured to determine by use of the measuring device of a first distance between the first lens and the first eye of the user; and adjust the first distance based on the determined distance between the first lens and the first eye of the user to correspond to a focal length of the first eye by generating control signals to the one or more actuators to prompt the actuator to move the first lens in the at least one of the plurality of directions.

[0025] Optionally, in the preceding aspect, subsequent to adjusting the first distance, the controller is further configured to: re-determine the first distance; calculate combined focal length of a system of the first eye and the first lens with the first lens at the redetermined first distance; and render images for the immersive display based on the re-determined first distance to maintain a viewing perspective as the focal length of the first lens is changed.

[0026] Optionally, in the preceding two aspects, the controller is further configured to: determine by the measuring device a gaze of the user wearing the immersive display; and adjust a focal length of the first lens in response to the determined gaze.

[0027] Optionally, in the preceding aspect, the first lens comprises a liquid crystal layer and the controller is further configured to: adjust the focal length of the first lens by adjusting a refractive index of the liquid crystal layer.

[0028] In other aspects, an eyeglass system comprises: a first lens; a frame configured to place the first lens at a first distance in front of a first eye of a user; an immersive display, the first lens located between the immersive display and the first eye; a measuring device coupled to the frame and configured to measure a distance between the first lens and the first eye of the user; and a controller configured. The controller is configured to: determine by use of the measuring device of the distance between the first lens and the first eye of the user; and based on the determined distance, adjust one or both of the displayed image size for the digital display or the focal length of the first lens to maintain the user’s view when the distance changes.

[0029] In other aspects, an eyeglass system comprises: a first lens and a frame configured to place the first lens at a first distance in front of a first eye of a user, the frame including a first actuator configured to move the first lens in at least one of a plurality of direction. The eyeglass system also includes: a measuring device coupled to the frame and configured to measure a distance between the first lens and the first eye of the user; and a controller configured to: determine by use of the measuring device of the distance between the first lens and the first eye of the user; and adjust the first distance based on the determined distance between the first lens and the first eye of the user by generating control signals to the first actuator to prompt the first actuator to move the first lens in at least one of the plurality of directions. [0030] Optionally, in the preceding aspect, the eyeglass system also includes: a second lens, wherein the frame is further configured to place the second lens at a second distance in front of a second eye of the user. The frame further comprises: a second actuator configured to move the second lens in at least one of the plurality of direction; a first leg including the first actuator; a second leg including the second actuator; and a cross-member connecting the first and second leg and holding the first lens and second lens. The measuring device is further configured to measure a distance between the second lens and the second eye of the user. The and controller is further configured to: determine by use of the measuring device of the distance between the second lens and the second eye of the user; and adjust, independently of the first distance, the second distance based on the determined distance between the second lens and the second eye of the user by generating control signals to the second actuator to prompt the second actuator to move the second lens in the at least one of the plurality of directions.

[0031] Optionally, in the preceding aspect, the frame also includes: a third actuator in the cross-member configured to charge a separation between the first lens and the second lens. The measuring device is further configured to measure an interpupi llary distance between the first eye of the user and the second eye of the user. The controller is further configured to: determine by use of the measuring device of the interpupillary distance; and adjust the interpupillary distance based on the determined interpupi llary distance by generating control signals to the third actuator to prompt the third actuator to change the separation between the first lens and the second lens.

[0032] Optionally, in the preceding two aspects, the frame also includes: a head strap connectable to the cross-member, the first leg, and the second leg; and a third actuator to charge a position of the cross-member relative to the head strap. The controller is further configured to adjust the position of the cross-member relative to the head strap by generating control signals to the third actuator to prompt the third actuator to change the position of the cross-member relative to the head strap.

[0033] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the Background.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Aspects of the present disclosure are illustrated by way of example and are not limited by the accompanying Figures for which like references indicate elements.

[0035] Figures 1A and 1 B are views of eyeglasses, in accordance with some embodiments.

[0036] Figure 2 is a block diagram of eyeglasses, in accordance with some embodiments.

[0037] Figure 3 illustrates the idea of vertex distance, which is an important concept in the following discussion.

[0038] Figures 4A and 4B illustrate some features of example embodiments for perspective-invariant varifocal eyeglasses.

[0039] Figure 5 illustrates an example of a liquid crystal gradient-index (GRIN) lens that can be used in embodiments of the optical system.

[0040] Figure 6 illustrates the unity of rendering binocular display.

[0041] Figure 7 illustrates an arrangement for an embodiment of an immerse display.

[0042] Figure 8 is a diagram of a two lens system to illustrate parameters involved in the example embodiments.

[0043] Figure 9 is a schematic representation of an embodiment for an immersive display system.

[0044] Figure 10 is a flowchart of an embodiment for the operation of the eyeglass system. [0045] Figures 11 and 12 respectively present embodiments of perspectiveinvariant varifocal eyeglasses for vision correction and for immersive displays.

[0046] Figures 13A-13C provide more detail on embodiments for eyeglasses with motor-driven actuators to adjust lens distances.

DETAILED DESCRIPTION

[0047] The following presents a perspective-invariant system, which maintains the focal length of the overall viewing system to be the same as that of a viewer’s eyes’ natural focal length, while varying the focus of the eyeglasses. Such a system can be realistic to our human natural vision and provide a gaze contingent, immerse 3D displays and eyeglasses for presbyopic assistance, optimizing virtual reality and vision assistance for all users through gaze contingent and adaptive focus. For immersive display embodiments, the system can render the image on the display panel so that the viewing perspective (or size of the display) can stay the same even though the focal length of the display optics change.

[0048] The making and using of embodiments of this disclosure are discussed in detail below. It should be appreciated, however, that the concepts disclosed herein can be embodied in a wide variety of specific contexts, and that the specific embodiments discussed herein are merely illustrative and do not serve to limit the scope of the claims. Further, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of this disclosure as defined by the appended claims.

[0049] Figures 1A and 1 B are views of a pair of eyeglasses 100, in accordance with some embodiments. The pair of eyeglasses 100 can be part of an immersive display (including head mounted virtual reality displays) or for vision assistance, such as presbyopia, where there is a physiological insufficiency of accommodation associated with the aging of the eye. Specifically, Figure 1A is a front view of the eyeglasses 100, and Figure 1 B is a side view of the eyeglasses 100. The eyeglasses 100 include a frame 102, lenses 104, and sensors 106. Although not separately illustrated in Figures 1A-1 B, the eyeglasses 100 also include a controller 112 (see Figure 2). The controller 112 may be disposed within any portion of or attached to the frame 102. As used here, eyeglasses are largely used interchangeably with an eyeglass system and can include systems such as immersive head mounted displays for virtual reality and augmented reality.

[0050] The frame 102 is an eyeglass frame that holds the lenses 104 in the proper position for the user (e.g., wearer) of the eyeglasses 100. The frame 102 can include a pair of rims that surround, or at least partially surround, and hold the lenses 104 in place, a bridge which connects the rims to one another, and earpieces connected to the sides of the rims. The frame 102 may be formed of any acceptable material such as plastic, metal, a combination thereof, or the like.

[0051] The lenses 104 are coupled to the frame 102. Specifically, the lenses 104 are held by the rims of the frame 102, such that the frame 102 extends at least partially around the lenses 104 and the bridge of the frame 102 is between the lenses 104. The lenses 104 may include displays that are used to display content such as an augmented reality overlay, a user interface (U I ), or the like to a user of the eyeglasses 100. As discussed below, in some embodiments the frame 102 can move the position of the lens 104 in response to the controller 112. The lenses 104 may be varifocal lenses. A varifocal lens is a lens (or set of lenses) that can vary focal length or vary the imagine plane.

[0052] The sensors 106 include one or more of visual sensors, audio sensors, position sensors, environment sensors, and the like. Examples of the sensors 106 include cameras such as wide-angle cameras, infrared cameras, or the like; depth sensors, such as MEMS (micro-electromechanical system) based Lidar (light detection and ranging); position sensors such as orientation sensors, magnetometers, or the like; motion sensors such as accelerometers, gravity sensors, gyroscopes, or the like; environment sensors such as light sensors, temperature sensors, humidity sensors, air pressure sensors, or the like; audio sensors such as microphones; medical sensors such as blood-oxygen sensors, brain wave sensors, pulse oximeter sensors, optical heart rate sensors, or the like; satellite navigation sensors such as global positioning system (GPS) sensors; or the like. Some or all of the sensors 106 are integrated or disposed within the frame 102. In some embodiments, the sensors 106 are disposed in the rims and bridge of the frame 102. The sensors 106 may be disposed symmetrically or asymmetrically around the frame 102, and may face towards and/or away from the user of the eyeglasses 100. For example, the sensors 106 may include cameras facing towards the user of the eyeglasses 100, which may be utilized to track the position(s) of the head, face, and/or eyes of the user. Similarly, the sensors 106 may include cameras facing away from the user of the eyeglasses 100, which may be utilized to track hand gestures of the user.

[0053] Figure 2 is a block diagram of the eyeglasses 100, in accordance with some embodiments. As noted above, the eyeglasses 100 also include a controller 112. The controller 112 is adapted to control the components of the eyeglasses 100 during operation. Controller 112 is adapted to control the components of the eyeglasses 100 by receiving input signals from the input devices of the eyeglasses 100 (e.g., the sensors 106) and transmitting output signals to the output devices of the eyeglasses 100 (e.g., the lenses 104). The controller 112 may include a control circuit, a processor, an application-specific integrated circuit, a microcontroller, or the like. For example, the controller 112 may include one or more processors and memories, such as non-transitory computer readable storage mediums, that store programming for execution by the processors. One or more modules within the controller 112 may be partially or wholly embodied as software and/or hardware for performing any functionality described herein. As subsequently described in greater detail, the controller 112 is adapted to control the focal length of the lenses 104 and the locating of the lens 104 by the frame 102.

[0054] In immersive display embodiments, a display 110 can also be included into the systems. The controller 112 can include the processing circuitry for the rending of the display images for display 110. The eye to lens distance can be incorporated in the algorithms for rendering of the images. Based on this distance, the controller 112 can calculate the overall focal length of the eyeglasses-eye system and render the image on the display panel so that the viewing perspective (or size of the display) stays the same even though the system adjusts the focal length of display optics.

[0055] Figure 3 illustrates the idea of vertex distance, which is an important concept in the following discussion. Figure 3 shows an eye 301 , with the front surface of the cornea (or the center of the pupil) indicated at 303, and an eyeglass lens 305. Vertex distance, deye, refers to the distance between the front surface of the cornea (or the center of the pupil) 303 and the back surface of the eyeglass lens 305. When the distance deye between the eye and the lens changes, it alters the magnification and the position of the lens relative to the eye, which can impact the visual prescription. Changes in the vertex distance deye can lead to alterations in visual acuity and image magnification. For example, if the vertex distance is shorter than the assumed value, it can result in increased magnification and reduced field of view. On the other hand, a longer vertex distance may lead to decreased magnification.

[0056] Figures 4A and 4B illustrate some features of example embodiments for perspective-invariant varifocal eyeglass system. These figures are a top view of a left eye 401 L and a right eye 401 R with respective front cornea surfaces 403R and 401 R. The eyes 401 L and 401 R respectively are looking though left and right lens 405 L and 405R with corresponding optical axes 407L and 407R. In Figure 4A, each eye 401 L/401 R is looking straight out along optical axis 407L/407R of the corresponding lens 405L/405R, whose surfaces nearest the corresponding eye are at the distance deye.

[0057] In Figure 4B, the eyes 401 L/401 R now have their gaze focused on a point X. As used here, gaze refers to where each of the eyes are looking, both in terms of direction and distance, which is reflected in the eye’s focus. The gaze from eye 401 L to point X is along line 409L that, typically, will not align with the optical axis 407L of lens 405L. Similarly, the gaze from eye 401 R to the point X is along line 409R that, typically, will not align with the optical axis 407R of lens 405R. The angle of the rays 409L and 409R, along with the eye-to-eye separation, will be a triangle in 3D space with the point X at the third vertex. The distance between the left eye 401 L and the left lens 405L is deyeL and the distance between the right eye 401 R and the right lens 405R is deyeR, where, depending on the gaze and geometry of the lens and eyes may be the same or somewhat different for the two eyes.

[0058] In the perspective-invariant varifocal eyeglasses embodiments presented here, the curvature radius of the lens 405L and 405R can be adjusted to vary the eyeglass’ focal lengths. While changing the curvature of the lens, the system maintains the eye-pupillary-axis distance deye between the eye anterior cornea and eyeglasses lens curved surface. In a typical embodiment, this will maintain deye within a range of around to 16mm, although in some embodiments this will be of a lesser range (e.g., 12-14mm) or larger range (e.g., 8-18mm).

[0059] Figure 5 illustrates an example of a liquid crystal gradient-index (GRIN) lens that can be used in embodiments of the optical system. Rather than change the focal length of a lens by changing its curvature, a liquid crystal GRIN lens can be a flat lens whose focal length is changed by altering the gradient of the refractive index of the lens material by the controller 112. Such lens do not have the aberrations that are typical of traditional spherical lens.

[0060] Figure 5 shows a focal point X located at a focal plane a distance do from the outward facing (i.e. , away from the eye) surface of the LC lens. The front of the LC lens is a distance d _g from the cornea of the eye 501 , which is in turn a distance di from the central plane of the eye’s crystalline lens. The retina at the back of the eye 501 is distance d2 from the plane of the crystalline lens. The gaze from the cornea passes through the crystalline lens and converges at the point X. Within the eye 501 , the crystalline lens forms the image of the point X to converge on the retina. For the flat liquid crystal GRIN lens of Figure 5, deye is the distance between anterior cornea and mid-plane of the lens.

[0061] The liquid crystal (LC) lens in the embodiment of Figure 5 has an outer portion 521 and inner portion 523 that can electrically tuned by biasing the lens by the controller 112 to change the indices of refraction of the two portions. When the LC GRIN lens is unbiased and off and the eye’s crystalline lens relaxed, the lens powers of both lens are zero, the farthest point the eye 501 can see is at some distance do. When the LC lens is still off, the eye can see at a near point under curvature of the crystalline lens; and when the LC lens is turned on as a positive lens, this nearest point shifts inward toward the eye 501 . When the LC lens is on and operated as a negative lens, the farthest point the eye can see is moved out further than the distance do. By altering the bias levels on the portions 521 and 523 in this way, the focal length of the LC lens can be varied continuously between a range of positive and negative powers by the controller 112 in the eyeglasses 100 based on an user’s gaze.

[0062] In addition to altering the power of the lenses for the eyeglasses, in other aspects the controller 112 can use the sensors 106 to measure the vertex distance deye from each lens to the corresponding eye adjust this distance. More specifically, as discussed further below, the controller can adjust deye based on the eye’s focal length.

[0063] There are several ways to measure the vertex distance, deye. In some embodiments, the sensors 106 can include a pupilometer. A pupilometer is a device used to measure the distance between the centers of the two pupils accurately. It is commonly used to determine the interpupillary distance (IPD), but it can also be used to measure the vertex distance deye.

[0064] Other embodiments can alternately, or additionally, use a near eye camera as part of the sensors 106. By using the near eye camera, the sensors 106 can capture the image or data that shows the distance from the front surface of the cornea (or center of the pupil) to the back surface of the eyeglass lens. The device will provide the vertex distance measurement based on the captured data. A single camera can focus to eye surface and to glasses surfaces separately in order to determine the distance.

[0065] Other embodiments can alternately, or additionally, use a depth sensor as part of the sensors 106. The depth sensor can be a MEMS (micro-electromechanical system) based Lidar (light detection and ranging) to both identify the x-y location of the eye pupil and the distance between the eye and eyeglasses (as shown in figure 4B). A depth camera can be activated to capture an image or depth map of the eye and eyeglass lens. The camera can use its depth-sensing capabilities to measure the distance between the front surface of the cornea (or center of the pupil) and the back surface of the lens. By performing eye detection, depth data analysis, and depth data of glasses, the disparity between the depth data obtained from the pupil and the eyeglasses signifies the vertex distance deye.

[0066] Figure 6 illustrates the unity of rendering binocular display, such as would be used for the eyeglasses 100. A binocular image is a pair of images that are viewed simultaneously through a binocular vision system, such as viewers eyes, where two pin hole cameras model with the same parameters to simulate human’s eyes. In Figure 6 left and right eyes 601 L and 601 R. When viewing a display, the eyes will be a distance d to the monitor 631 and separated by an interpupillary distance IPD. The locating of the lens within the eyeglasses 100 by the controller 112 can incorporate the design of a human binocular vision model. For example, parameters can include average eye height of a human (men=1635mm, woman=545mm), average IPD of a human (between 50 - 75 mm, with an average of 63mm), and average eye field of vision (142 degrees horizontal, 165 degrees vertical).

[0067] The embodiments for perspective-invariant varifocal eyeglasses presented here can be used both for vision correction, such as for presbyopes, and for immersive displays, such as for virtual reality or augmented reality glasses or head mounted displays. Figure 7 considers the image formation geometry for the immersive display case in more detail.

[0068] Figure 7 illustrates a side view of an arrangement for an embodiment of an immerse display. An eye 701 is viewing a micro display 741 of height h’ through a lens 705 of focal length f that is separated from the micro display 741 by a distance of d’, where the micro display 741 and lens 705 are part of a head mounted display HMD 739. In the side view of Figure 7, only the one eye and corresponding micro display and lens are shown, but a similar lens and micro display can be include in HMD 739 for the other eye. The eye 701 will perceive a virtual image 743 of height h at a distance from the lens of D. From the Gaussian thin lens formula, these parameters are related as (1/D) + (1/d’) = (1/f), or D = ((1/f) - (1/d’)) ^-1 . The corresponding magnification M can be expressed as M=f/(f-d’) or h=Mh’.

[0069] In a near-eye binocular display such as Figure 7, the image plane becomes the virtual image plane 743. The rendered display on the micro display panel 741 relates to d _eye . In most cases, since d _eye «d, system designs ignore the parameter d _eye . For example, in typical set of values are d _eye =10mm, d=500mm. However, for the high resolution displays presented here, the value of deye is measures and incorporated into image rendering on display panel 741.

[0070] Figure 8 is a diagram of a two lens system to illustrate parameters involved in the example embodiments. In Figure 8, the front lens a is the lens of the eyeglasses, such as the liquid crystal lens of Figure 5 or lens 705 of Figure 7, and has a focal length f _a , or reciprocal focal length cp _a . The back lens is the crystalline lens of the eye and has a focal length fb, or reciprocal focal length cpb. The diagram also shows the principal planes of both lens and also the first principal plane of the combination at Pi and second principal plane of the combination at P2. A ray incident from the left will converge at the focal point that, if the system is in focus, will converge on the retina of the eye. The distance between the second principal plane (or focal plane or Fourier plane) of lens a and the first principal plane of lens b is d and the distance between the second principal plane of lens b and the focal point is B.

[0071] The effective focal length of the lens system is fab:

For the case here, when lens b is the lens of the eye and lens a is the lens of the eyeglasses, d=deye. Other relationships between the parameters are f _a =(d fab) I (fab - B) and fb=(-d B) I (fab- B- d). Considering the expression for fab, the distance from eyeglasses to eye d=deye is critical: when d=fb, eyeglasses is at eye’s front focal plane (or Fourier plane) and fab=fb and the system’s focal length is independent the variation of fa. As lens b is the crystalline lens of the eye, when deye— feye the effective focal length of the system is feye.

[0072] Referring back to Figure 7, there are two ways to obtain varifocus, either by varying the plane distance d’ of micro display 741 or varying the focal length of lens 705. When lens is placed at the eye’s front focal plane, deye=feye, and the combined focal length keeps constant at feye even as focal length f of the lens 705 varies. This arrangement still allows for the virtual image depth D. As D = ((1/f) - (1/d’)) ^-1 , when f of lens 705 (corresponding to f _a in the discussion of Figure 8) varies, the second principle plane of the combined position (P2 in Figure 8) also varies, so that the distance d’ varies. Consequently, varying d’ and varying f have the same effect when deye ⁼ feye. By having the sensors 106 monitor the viewer’s gaze by eye tracking to determine parameters such as the interpupillary distance and gaze angle, the controller 112 can then adjust the focal length of the lens, such as the liquid crystal GRIN lens of Figure 5, to change the virtual image depth D for the viewer. In this way, the image from each display on the retina will stay the same, adding to the realism of the display presentation. [0073] The embodiments presented here use an image rendering algorithm that represents the display optics and the eye’s crystalline lens as a simple single lens. The overall display to retina magnification depends on the system focal length, while the system focal length depends on the parameter deye. The is represented schematically in Figure 9.

[0074] Figure 9 is a schematic representation of an embodiment for an immersive display system where the eyeglass system’s lens and the eye’s lens are treated as a single simple lens by having deye equal to the eye’s focal length. The eye’s focal length can be set on standard values from physiological measurements, such as a default value that in some embodiments could be fine turned, could be a user’s measure value that could be entered into the controller 112, or, if a sensor 106 is available to measure the user’s value, the system could determine the value. For example, an eye’s focal length varies with accommodation and dispersion and is typically in the range of 14.5 to 17.0mm so that, for example, for green light (wavelength 550nm), 15.6mm could be used as a default value for looking at distance 300mm away or 16.5mm could be used as a default value when looking at 6000mm away or beyond.

[0075] . The combined right side display optics and eye system 901/905R form image from a right display 941 R on the right eye retina. Similarly, the left side display optics and eye system 901/905L form image from a left display 941 L on the left eye retina. The viewer perceives a virtual image 943 with a magnification ratio M that then depends on system’s focal length f, which is related to lens to eye distance deye.

[0076] Figure 10 is a flowchart of an embodiment for the operation of the eyeglass system. Referring to Figures 1A-2, the flow can begin at 1001 with controller 112 using the sensors to measure, once the viewer is wearing the eyeglass system 100 (including displays in the case of an immersive display such as a head mounted display), the distance deye between each lens 104 and the user’s corresponding eye. The sensors 106 for determining deye can be one or more of a pupilometer, a near eye camera, and depth sensor. Based on the values for deye and the focal length feye of the eye, in 1003 the controller can then adjust the distance deye to correspond to feye. The focal length feye of the eye can be a default value set on standard values from physiological measurements, which in some embodiments could be fine turned, could be a user’s measure value that could be entered into the controller 112, or, if a sensor 106 is available to measure the user’s value, the system could determine the value. For example, an eye’s focal length varies with accommodation and dispersion and is typically in the range of 14.5 to 17mm so that, for example, for green light (wavelength 550nm), 15.6mm could be used as a default value for looking at distance 300mm away or 16.5mm could be used as a default value when looking at 6000mm away or beyond.

[0077] To adjust deye, the controller can include mechanical motors within the frame 102 to move the lens to adjust deye. In some embodiments, this can alternately or additionally be manually adjustable by the user, such as by a knob to adjust the distance. The knob may be coupled to a mechanical actuator structure to move the lens. Alternatively, the knob may be coupled to circuitry that generates voltage signals that drive one or more motors to move the lens in a desired direction. In embodiments with a display, once the deye adjustment is made the display can render the image so that the image size on the retina stays the same as the viewer’s gaze changes. The sensors 106 can periodically or on an ongoing basis monitor the deye value and update the lens position if needed, such if the eyeglasses shifts due to user movement. The measurements can be made with high resolution, such as at the millimeter level, in order to render the best quality images for a given distance.

[0078] In some embodiments with an immersive display, such as a head mounted virtual reality or augmented reality embodiment, the eye to lens distance can be incorporated into the algorithms used by the controller 112 to render the images. The distance as determined in 1001 can be used or, to provide a more accurate determination, at 1005 the distance can be re-measured after the adjustment at 1003. In either case, based on the distance the controller 112 can calculate the overall focal length of the eyeglasses-eye system and incorporate this at 1007 into the algorithms the controller uses to render the image on the display panel 110, so that the viewing perspective (or size of the display) stays the same as the controller 112 adjusts the focal length of display optics.

[0079] As the viewer uses the eyeglass system 100, the sensors 106 can also monitor the users gaze at 1009. For example, by a combination of interpupillary distance and gaze angle, the distance D of a virtual image can be determined and the focal length of the lens 104 adjusted accordingly at 1011 . In some embodiments, the curvature of the lens can be adjusted by the controller 112 or, in the case of a liquid crystal lens, the controller 112 can change the bias on the lens to alter its index of refraction. Some embodiments can also include indirect distance measurement, in collaboration with user viewing experience and image rendering for users who may want to have a somewhat different view.

[0080] In some embodiments, in addition to or instead of adjusting deye at step 1003, based on the distance measure at 1001 , 1005, or both, in an immersive display the displayed image size for the digital display can be adjusted at 1007 and/or the focal-length variation of the first lens can be adjusted at 1011 so that user’s view remains the same even when the lens moves. Consequently, in addition to or instead of adjusting a hardware distance, the system can also adjust the software through image rendering or the lens’ focal length variations.

[0081] Figures 11 and 12 respectively present embodiments of perspectiveinvariant varifocal eyeglasses for vision correction and for immersive displays. Much of the discussion above focused on an immersive display, but Figure 11 illustrates the application of the techniques described above to eyeglasses for vision correction. In this example, the lens 1105 is a plano-concave lens (i.e. , with a negative focal length) for presbyopes assistance, with the lens 1105 at a distance deye from the eye 1101 along the visual axis. The distance deye corresponds to the focal distance of the eye 1101 and a typical range is 10-16mm.

[0082] Figure 12 illustrates the application of the techniques described above to an eyeglass system including a display 1241. For example, the eyeglass system could be a virtual reality or augmented reality headset. The lens 1205 is a plano-convex lens (i.e., with a positive focal length) separated from the display 1241 by a spacer 1249. The surface of the lens 1205 is again at a distance deye that corresponds to the focal distance of the eye 1201 and has a typical value in the range of 10-16mm. Although shown as a single layer lens in Figure 12, lens 1205 can also be more complicated, such as 2-element or 3-element pancake lens.

[0083] Figures 13A-13C provide more detail on embodiments for eyeglasses with motor-driven actuators to adjust lens distances. Figure 13A is a side-view of an embodiment of an eyeglass frame 102 similar to Figure 1 B, but now explicitly showing a motor driven actuator 1301 to adjust the distance L between the leg and frame. The controller 112 can be connected to prompt the actuator 1301 adjust the distance between the lens and user’s eyes as described above. The description above has focused on moving the lens in the single direction between the users eyes and the lens, but, additionally, in some embodiments the controller 112 can prompt the actuator to move the lens in other directions to, for example, maintain alignment of the optical axis between the eyes and the lens. The side view of Figure 13A shows only the single actuator 1301 , which, depending on the embodiment, may move the frame relative to both legs together or only move the frame relative to the one leg. Other embodiments may have independently controllable actuators for the left and right sides.

[0084] Figure 13B presents an oblique view of an embodiment of an eyeglass, where this can be an alternate view of the embodiment of Figure 13A or can include independent actuators 1311 and 1312 for both the left and right legs of the frame 102 and, optionally, an actuator 1313 in the cross-member holding lens 104L and 104R to adjust the spacing between the left lens 104L and the right lens 104R. The controller 112 can use separate motor-driven actuators to adjust the distances independently, where adjusting L1 to adjust the distance between the right portion of glasses to right eye, adjusting L2 to adjust the distance between the left portion of glasses to left eye, and L3 adjusts the intra-pupil distance. Although each of the actuators 1311 , 1312, and 1313 many each only move in one in some embodiments, in other embodiment one or more may provide movement in multiple directions, not just independently deye for each eye and the interpupillary distance, but also shift the lens to maintain alignment of the optical axis for the left and right lens-eye system. Optionally, a head strap 1317 between the legs attachable on the back side of head can be used to secure the positioning of the eye glass system frame 102 with respect to the user’s head.

[0085] In addition to being prompted to change L1 , L2, and/or L3 by the controller 112, the actuators 1311 , 1312, and 1313 can alternately or additionally be manually adjustable by the user. This can allow the user to fine tune the adjustments by the controller 112 or make the adjustments themselves. In some embodiments, the controller 112 can provide the user with feedback based on the user’s adjustments, such as indicating if the lenses distances to the eye are at, greater than, or less than the focal length of the eyes. Depending on the embodiment, the feedback can include visual, auditory, or tactile (e.g., vibrations) feedback to allow the user to determine whether deye for each eye in at, above, or below the target distance.

[0086] Figure 13C presents a further embodiment that, in addition to the features of Figure 13B, includes an overhead portion 1319 for the head straps to fasten the glasses more securely on the user’s head. Besides the ability to adjust the distance L1 , L2, and L3, the overhead straps 1319 can fasten the glasses and the additional motor-driven actuator1314 can adjust the distance L4 to adjust the glasses position up and down on the user’s head. The controller 112 can adjust the position of the cross-member relative to the head strap based on one or more of the measured deye values and interpupil lary distance or based user input, either through the controller or manually, for factors such as comfort.

[0087] For any of the embodiments presented here, the eyeglass system can provide a “varifocal” technology that provides correct depth of focus (versus a single fixed focus), thereby enabling clearer and more comfortable vision for extended periods of time. The system’s resolution can approaches and ultimately exceed 20/20 human vision. Distortion correction can also help address optical aberrations, like color fringes around objects and image warping, that are often introduced by viewing optics. Combined with the use of high dynamic range technology for displays, the system can expand the range of color, brightness, and contrast you can experience in immersive virtual reality viewing devices.

[0088] It is understood that the present subject matter may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this subject matter will be thorough and complete and will fully convey the disclosure to those skilled in the art. Indeed, the subject matter is intended to cover alternatives, modifications and equivalents of these embodiments, which are included within the scope and spirit of the subject matter as defined by the appended claims. Furthermore, in the following detailed description of the present subject matter, numerous specific details are set forth in order to provide a thorough understanding of the present subject matter. However, it will be clear to those of ordinary skill in the art that the present subject matter may be practiced without such specific details. [0089] Aspects of the present disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatuses (systems) and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable instruction execution apparatus, create a mechanism for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

[0090] The description of the present disclosure has been presented for purposes of illustration and description but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The aspects of the disclosure herein were chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure with various modifications as are suited to the particular use contemplated.

[0091] For purposes of this document, each process associated with the disclosed technology may be performed continuously and by one or more computing devices. Each step in a process may be performed by the same or different computing devices as those used in other steps, and each step need not necessarily be performed by a single computing device.

[0092] Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.