Patent Publication Number: US-10761328-B2

Title: Display glasses using meta-surface planar lens

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention generally relates to the area of optical lens and more particularly relates to architecture and designs of optical lens using flat optical lens, where the optical lens is advantageously used in wearable display glasses for various applications including virtual reality augmented reality with 3D capabilities. 
     Description of the Related Art 
     Virtual Reality or VR is generally defined as a realistic and immersive simulation of a three-dimensional environment created using interactive software and hardware, and experienced or controlled by movement of the body. A person using virtual reality equipment is typically able to look around the artificially generated three-dimensional environment, moves around in it and interacts with features or items that are depicted on a screen or in goggles. Virtual realities artificially create sensory experiences, which can include sight, touch, hearing, and, less commonly, smell. 
     Augmented reality (AR) is a technology that layers computer-generated enhancements atop an existing reality in order to make it more meaningful through the ability to interact with it. AR is developed into apps and used on mobile devices to blend digital components into the real world in such a way that they enhance one another, but can also be told apart easily. AR technology is quickly coming into the mainstream. It is used to display score overlays on telecasted sports games and pop out 3D emails, photos or text messages on mobile devices. Leaders of the tech industry are also using AR to do amazing and revolutionary things with holograms and motion activated commands. 
     The delivery methods of Virtual Reality and Augmented Reality are different when viewed separately. Most 2016-era virtual realities are displayed either on a computer monitor, a projector screen, or with a virtual reality headset (also called head-mounted display or HMD). HMDs typically take the form of head-mounted goggles with a screen in front of the eyes. Virtual Reality actually brings the user into the digital world by cutting off outside stimuli. In this way user is solely focusing on the digital content being displayed in the HMDs. Augmented reality is being used more and more in mobile devices such as laptops, smart phones, and tablets to change how the real world and digital images, graphics intersect and interact. 
     In reality, it is not always VR vs. AR as they do not always operate independently of one another, and in fact are often blended together to generate an even more immersing experience. For example, haptic feedback, which is the vibration and sensation added to interaction with graphics, is considered an augmentation. However, it is commonly used within a virtual reality setting in order to make the experience more lifelike though touch. 
     Virtual reality and augmented reality are great examples of experiences and interactions fueled by the desire to become immersed in a simulated land for entertainment and play, or to add a new dimension of interaction between digital devices and the real world. Alone or blended together, they are undoubtedly opening up worlds, both real and virtual alike. 
       FIG. 1A  shows an exemplary goggle now commonly seen in the market for the application of delivering or displaying VR or AR. No matter how a goggle is designed, it appears bulky and heavy, and causes inconvenience when worn on a user. Further most of the goggles cannot be seen through. In other words, when a user wears a goggle, he or she would not be able to see or do anything else. Thus, there is a need for an apparatus that can display the VR and AR but also allows a user to perform other tasks if needed. 
     Various wearable devices for AR/VR and holographic applications are being developed.  FIG. 1B  shows a sketch of HoloLens from Microsoft. It weights 579 g (1.2 lbs). With such weight, a wearer won&#39;t feel comfortable when wearing it for a period. Indeed, what is available in the market is generally heavy and bulky in comparison to normal glasses. Thus there is a further need for a wearable AR/VR viewing or display device that looks similar to a pair of regular glasses but is also amenable to smaller footprint, enhanced impact performance, lower cost packaging, and easier manufacturing process. 
     One of the components that make the weight in a goggle is the lenses. Although light materials have been tried, the thickness of the lens or lenses is significant in view of the lenses used in a pair of regular glasses. Thus there is a further need for a lens or lenses that can be made thinner and lighter so that a wearing device for the AR/VR applications could be made lighter or more similar to the regular glasses. 
     A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis. Lenses are made from materials such as glass or plastic, and are ground and polished or moulded to a desired shape (e.g., to fit into an optical frame). Unlike a prism which refracts light without focusing, a lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material while a compound lens consists of several simple lenses (elements), usually arranged along a common axis.  FIG. 2A  shows an exemplary compound lens for use in AR/VR glasses. As shown in  FIG. 2A , there are at least five individual lenses arranged in line-up along an optical axis. The spaces between the lenses are filled up with air which has a refractive index of 1.0. These individual lenses are of different shapes and made of materials of different refractive indices, arranged one after the other with an optical axis. A single lens is subject to the optical aberrations that can be compensated for to a great extent by using a combination of simple lenses with complementary aberrations, thus the compound lens. It can be appreciated that the compound lens of  FIG. 2A , as most lenses in practical uses, are bulky and expensive. As wearable or portable devices are getting smaller in sizes, the lenses for imaging or video are becoming a challenge to fit into such devices.  FIG. 2B  illustrates the use of a compound lens on iPhone X, where the lens has to stick out from the back of the device because of its relative bulky size of the compound lens in the phone. In addition, the bulky size not only increases the lens cost, it also adds the weight. It would be desirable to have a single lens that achieves what a compound lens may achieve. 
     Despite tremendous interest in planar lenses in the visible spectrum, there has been no solution that simultaneously satisfies the demands for high numerical aperture (NA) and efficiency, let alone for high end imaging applications. The Capasso Group at Harvard University introduced a breakthrough solution for this problem using titanium dioxide-based metasurfaces that allow the miniaturization of conventional refractive optics into planar structures. The Harvard group shows that high-aspect-ratio titanium dioxide metasurfaces can be fabricated and designed as metalenses with NA=0.8. Diffraction-limited focusing is demonstrated at wavelengths of 405 nm (blue), 532 nm (green), and 660 nm (red) with corresponding efficiencies of 86, 73, and 66%. The metalenses can resolve nanoscale features separated by subwavelength distances and provide magnification as high as 170×, with image qualities comparable to a state-of-the-art commercial objective. However, as admitted by the group, it is still in the research phase, there are no such planar lenses available yet for commercial use. 
     SUMMARY OF THE INVENTION 
     This section is for the purpose of summarizing some aspects of the present invention and to briefly introduce some preferred embodiments. Simplifications or omissions in this section as well as in the abstract and the title may be made to avoid obscuring the purpose of this section, the abstract and the title. Such simplifications or omissions are not intended to limit the scope of the present invention. 
     The present invention is generally related to the designs of display devices using one or more planar lenses. According to one aspect of the present invention, a planar lens includes at least a substrate and a plurality of nanosized studs. As the name suggests, the nanosized studs are tiny transparent objects arranged in a pattern on the substrate. Depending on the implementation, the objects may be in different heights, spaced evenly or unevenly and oriented towards or outwards a focal point. According to another aspect of the present invention, the nanosized studs are formed on the substrate by electron beam lithography and atomic layer deposition. 
     According to still another aspect of the present invention, the nanosized studs are formed in layers on the substrate by electron beam lithography and atomic layer deposition. Depending on the purpose of the planar lens, the layers are in different materials, each of the materials reacts to or interacts with colors of a light differently. 
     According to still another aspect of the present invention, a display device includes an optical lightguide provided to receive an image and function as a medium to form the image therein. The lightguide is coated with the planar lens, wherein the image is seen through the planar lens. When the nanosized studs are properly structured in a pattern, the image can be seen enlarged through the planar lens. 
     According to another aspect of the present invention, the material used to form the nanosized studs includes a metamaterial being a material engineered to have a property that is not found in nature. The metamaterial has a relatively high refractive index at least greater than 2 and a level of stability, as well as high visible light transmittance. In one embodiment, the metamaterial is made from assemblies of multiple elements fashioned from composite materials. 
     According to yet another aspect of the present invention, the nanosized studs may be structured in different metamaterials, each of the metamaterials can be designed to react differently to the colors (wavelengths), phases and/or magnitudes, and deposited on top of each other, followed by etching process to shape/arrange the nanosized studs in a predefined volume/pattern. In addition, planar lenses with different characteristics can be stacked, matching the functions of a compound glass lens. 
     The present invention may be implemented as an apparatus, a method, a part of system. Different implementations may yield different benefits, objects and advantages. In one embodiment, the present invention is a display apparatus for displaying multimedia, the display apparatus comprises a planar lens system having at least one planar lens including a substrate and a plurality of nanosized studs, wherein the nanosized studs are formed on the substrate by electron beam lithography and atomic layer deposition; and an optical lightguide, receiving an image and forming the image therein, integrated with the planar lens system, wherein the image is seen through the planar lens system. Depending on implementation, the planar lens system may have only one single planar lens or multiple planar lenses stacked along an optical axis of the planar compound lens or system. 
     According to another embodiment, the present invention is a display apparatus for displaying multimedia, the display apparatus comprises: a planar lens system having at least one planar lens including at least a substrate, wherein a plurality of nanosized studs are formed on the substrate by electron beam lithography and atomic layer deposition, and an image source producing an image. The image source is integrated with the planar lens system, the image is then seen through the planar lens system, where the image is viewed either smaller or enlarged in size. 
     One of the objects in the present invention is to have a display device integrated with such a planar lens to reduce the physical size of the display device. 
     There are many other objects, together with the foregoing attained in the exercise of the invention in the following description and resulting in the embodiment illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
         FIG. 1A  shows an exemplary goggle now commonly seen in the market for the application of delivering or displaying VR or AR; 
         FIG. 1B  shows a sketch of HoloLens from Microsoft; 
         FIG. 2A  shows an exemplary compound lens for use in AR/VR glasses; 
         FIG. 2B  illustrates the use of a compound lens on iPhone X, where the lens has to stick out from the back of the device because of its relative bulky size in the phone; 
         FIG. 3A  shows a planar lens according to one embodiment of the present invention, the planar lens includes a transmissive optical substrate and a plurality of nanosized studs; 
         FIG. 3B  illustrates one exemplary structure in which the nanosized studs are formed oriented towards the center of the planer lens, resulting in a focusing or reducing lens; 
         FIG. 3C  illustrates one exemplary structure in which the nanosized studs are oriented outwards from the center of the planer lens, resulting in a defocusing or enlarging lens; 
         FIG. 3D  shows an exemplary design of the nanosized studs according to one embodiment of the present invention; 
         FIG. 3E  shows an exemplary design of stacking two or more planar lenses to match the functions in a compound lens, where each of the planar lenses is designed in different optical characteristics; 
         FIG. 4A  shows a user wears a pair of glasses for AR/VR applications, where the glasses include at least one optical lightguide provided to centralize an image from a projection source, and the image is seen by the user through an exemplary lens of  FIG. 3A ; 
         FIG. 4B  shows an exemplary lens that may be used in the glasses shown in  FIG. 4A ; 
         FIG. 4C  shows a configuration of using a planar lens in a pair of AR/VR glasses; 
         FIG. 4D  shows a light guide or lightguide (i.e., a waveguide) guides a projected image from a microdisplay; 
         FIG. 5A  shows an example for holographic applications that use refractive optics in AR setup; and 
         FIG. 5B  shows another improved design of  FIG. 5A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The detailed description of the invention is presented largely in terms of procedures, steps, logic blocks, processing, and other symbolic representations that directly or indirectly resemble an optical lens. The description and representations herein are typically used by those skilled in the art to most effectively convey the substance of their work to others skilled in the art. 
     Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Further, the order of blocks in process flowcharts or diagrams representing one or more embodiments of the invention do not inherently indicate any particular order nor imply any limitations in the invention. 
     Embodiments of the present invention are discussed herein with reference to  FIGS. 3A-5B . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes as the invention extends beyond these limited embodiments. 
     Referring now to the drawings, in which like numerals refer to like parts throughout the several views.  FIG. 3A  shows a planar lens  300  according to one embodiment of the present invention. The planar lens  300  includes a transmissive optical substrate  302  and a plurality of nanosized studs  304  that are thinner than a sheet of paper according to one embodiment. These nanosized studs  304  (e.g., 600 nm in length) are engineered to control the way in which light waves interact therewith. Depending on the implementation, the substrate  302  may be made flat or curved while the nanosized studs  304  are formed indifferent patterns. Different patterns focus different colors and bend lights with respect to the focal point, matching what happens in the glass lenses. 
     According to one embodiment, these nanosized studs  304  are formed by electron beam lithography and atomic layer deposition. According to another embodiment, the nanosized studs  304  are formed from so-called metamaterials. The nanosized studs  304  are structured to focus light across the visible spectrum. The setup allows them to magnify images up to 170 times with high resolution if the pattern of the nanosized studs  304  is properly structured and formed. 
     A metamaterial is a material engineered to have a property that is not found in nature. They are made from assemblies of multiple elements fashioned from composite materials such as metals or plastics. The materials are usually arranged in repeating patterns, at scales that are smaller than the wavelengths of the phenomena they influence. Metamaterials derive their properties not from the properties of the base materials, but from their newly designed structures. Their precise shape, geometry, size, orientation and arrangement gives them their unique properties capable of manipulating electromagnetic waves: by blocking, absorbing, enhancing, or bending waves, to achieve benefits that go beyond what is possible with conventional materials. In other words, appropriately designed metamaterials can affect waves of electromagnetic radiation or sound in a manner not observed in bulk materials. 
     According to one embodiment, amorphous titanium dioxide (TiO2) is used to be deposited onto a glass substrate (e.g., the substrate  302  of  FIG. 3A ) to make a nanosized studs  304 . In other embodiments, other inorganic materials which have a relatively high optic index, low absorption to visible and/or other electromagnetic wavebands may be used to form these nanosized studs  304 . According to one embodiment, vapor deposition and lithography are used to produce such nanosized studs  304 . The two most common deposition methods are physical vapor deposition (PVD) and chemical vapor deposition (CVD). Depending on the material being used, either one may be used to produce high quality, technologically advanced thin films in mass production. 
     In theory, any metamaterial (e.g., silicon, germanium, and tellurium) that is sensitive to visible light, near Infrared, UV, and etc. may be used to be deposited on a transparent substrate to structure the nanosized studs that may be arranged in hexagonal lattice, square lattice, and etc. According to one embodiment, a type of metamaterial that has transmittance (&gt;90%) and phase of the transmission (0˜2 π) may be used, such as iron oxides, ZrO2. Some heavy metal transitional metal oxides, such as tungsten oxides, tantalum oxides, niobium pentoxide, molybdenum trioxide, etc. have a relatively high refractive index (e.g., &gt;2) and a certain level of stability, as well as high visible light transmittance may be used as well. 
     The detailed structure of the nanosized studs  304  controls the functions of the planer lens  300  shown in  FIG. 3A . Depending on how the nanosized studs  304  are made, oriented, arranged in different heights, or spaced differently, the planer lens  300  may have different optical characteristics.  FIG. 3B  illustrates one exemplary structure in which the nanosized studs  304  are oriented towards the center of the planer lens  300 , resulting in a focusing or reducing lens.  FIG. 3C  illustrates one exemplary structure in which the nanosized studs  304  are oriented outwards from the center of the planer lens  300 , resulting in a defocusing or enlarging lens.  FIG. 3D  shows an exemplary design  310  of the nanosized studs according to one embodiment of the present invention. Three studs are shown to have been formed on a transparent substrate  312 . As an example, each of the studs is structured in five different layers L 1 , L 2 , L 3 , L 4  and L 5 . In other word, these five different metamaterials are deposited individually. It is assumed that a nanosized stud is of round in cross-section, the diameters of these five different layers may or may not be identical to compensate for various possible optical aberrations (e.g., astigmatism, barrel distortion, chromatic, aberration, coma, distortion, field curvature, petzval dondition, pincushion distortion, and spherical aberration). Depending on the implementation, the actual shape of a nanosized stud (or each of the layers in a cross-section) may be in nano-disk, rod, V-shape and etc. 
       FIG. 3E  shows an exemplary design  320  of stacking two planar lenses to match the functions in a compound lens, according to one embodiment of the present invention. It should noted that  FIG. 3E  shows only two planar lenses stacked to function what a compound glass lens does. The planar lenses in a compound lens are designed in different optical characteristics. As described above, a planar lens is typically in nanometer in thickness, thus a stack of planar lens is still significantly much thinner than a single glass lens, but delivering similar optical effects. 
     It is assumed that a first planar lens  322  in  FIG. 3E  is performing optical focusing, namely focusing an image impinged upon the planar lens  322  on the left. The image is focused onto a second planar lens  324  assumed to be designed to enlarge the image. Additional planar lens may be inserted between the first and second planar lens or before the first planar lens or after the second planar lens to compensate for various possible optical aberrations to fully match what a compound glass lens is structured, but in significantly reduced size in thickness. 
     Referring now to  FIG. 4A , it shows a user wears a pair of glasses  400  for AR/VR applications. The glasses  400  include at least one optical lightguide  402  provided to centralize an image from a projection source (not shown). In operation, an image is projected from the source into the optical lightguide  402 , where the image is formed therein and can be seen by the eye. According to one embodiment, the planar lens  300  of  FIG. 3A  may be used as a lens  404  and/or  406  enclosed in a frame  408 . Depending on where the lens is used, the lens  404  and  406  function differently by forming the nanosized studs  304  accordingly for the purpose of the lens. 
     As an example, when the lens  404  is used, the nanosized studs  304  on the substrate  302  may be formed in different heights and/or spaced unevenly to help the vision of the eye focused onto a display in the lightguide  402 . According to one embodiment, the nanosized studs  304  are oriented outwards from an optical axis line towards a center of the pupil to form an enlarging lens. As a result, the wearer of the glasses  400  can see an enlarged image through the lens  404 . When the lens  406  is used, the nanosized studs  304  on the substrate  302  may be oriented considerably towards the optical axis to form a tinted lens. 
     Referring now to  FIG. 4B , it shows an exemplary lens  460  that may be used in the glasses shown in  FIG. 4A . The lens  460  includes two parts, a prism  462  and an optical correcting lens or corrector  464 . The prism  462  and the corrector  464  are stacked to form the lens  460 . As the name suggests, the optical corrector  464  is provided to correct the optical path from the prism  462  so that a light going through the prism  462  goes straight through the corrector  464 . In other words, the refracted light from the prism  462  is corrected or de-refracted by the corrector  464 . In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. At least two of the flat surfaces must have an angle between them. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use a prism usually refers to this type. Prisms can be made from any material that is transparent to the wavelengths for which they are designed. Typical materials include glass, plastic and fluorite. According to one embodiment, the type of the prism  462  is not in fact in the shape of geometric prisms, hence the prism  462  is referred herein as a freeform prism or lightguide, which leads the corrector  464  to a form complementary, reciprocal or conjugate to that of the prism  462  to form the lens  460 . 
     On one edge of the lens  460  or the edge of the prism  462 , there are at least three items utilizing the prism  462 . Referenced by  467  is an imaging source that projects an image into the prism  462 . Examples of the imaging source may include, but not be limited to, LCoS, LCD, and OLED. The projected image is refracted in the prism  462  and subsequently seen by the eye  465  in accordance with the shapes of the prism  462 . In other words, a user wearing a pair of glasses employing the lens  462  can see the image being displayed through or in the prism  262 . According to one embodiment, the lens  462  is coated with a planar lens without significantly adding weight (e.g., the planar lens  300  of  FIG. 3A ) that is formed as an enlarging lens. As a result, the projected image formed in the prism  462  can be seen by the eye  465  enlarged by a few factors (e.g., 10 times or more). 
     Referring now to  FIG. 4C , it shows a configuration of using a planar lens in a pair of AR/VR glasses. An image source  410  projects an image onto a polarizing beam splitter (PBS)  412  that redirects the image towards the eye  414  via a planer lens  416 . Examples of the image source  410  may include, but not be limited to, LCOS, LCD, OLED, microdisplay and imaging medium. In the configuration in  FIG. 4C , the image source  410  provides an image directly to the PBS  412  or indirectly via an optics. The planar lens  416  enlarges the image slightly, provided the nanoside studs are formed properly on the substrate. As a result, the eye  414  sees an enlarged optical image through the PBS  412 , where the image appears far from the PBS  412 . 
       FIG. 4D  shows a light guide or lightguide  420  (i.e., a waveguide) guides a projected image from a microdisplay  422 . In one embodiment, an image from a microdisplay  422  is focused by optics  424  onto one end of the lightguide  420  that propagates the image to another end of the lightguide  420  where the image is seen by the eye through a planar lens  428 . It is assumed that the nanoside studs are formed properly on the substrate for enlarging purpose. As a result, the eye  426  sees an enlarged optical image  430  through the planar lens  428 , where the image  430  appears far from the lightguide  420 . 
       FIG. 5A  shows an example for holographic applications that use refractive optics in AR setup. It uses two full color holograms for such design on a thin photopolymer. The first one is a wavelength selective holographic spherical mirror that directs the image into the eye. The second one is a wavelength selective 45 degree holographic mirror. In one embodiment, the 45 degree mirror is tilted physically by 45 degrees to the second hologram. The display can be mounted above or to the side of the 45 degree mirror, but it must directly point at the mirror so the mirror reflects the signal. The light source can be LCD or LCOS and illuminated with LED&#39;s or Laser&#39;s. The light source can be positioned above or to the side of the 45 degree holographic mirror. A glass lens  502  is coated with a planar lens to enlarge the image that can be seen by the eyes. 
       FIG. 5B  shows another improved design of  FIG. 5A . This design  510  uses a transmissive LCoS (Liquid Crystal on Silicon) microdisplay that projects an image from the LCoS onto the cube. According to one embodiment, the LCoS is illuminated by R, G and B light sources to generate R, G and B color image sequentially. A glass lens  502  is coated with a planar lens to enlarge the image that can be seen by the eyes. 
     The present invention has been described in sufficient detail with a certain degree of particularity. It is understood to those skilled in the art that the present disclosure of embodiments has been made by way of examples only and that numerous changes in the arrangement and combination of parts may be resorted without departing from the spirit and scope of the invention as claimed. Accordingly, the scope of the present invention is defined by the appended claims rather than the forgoing description of embodiments.