Methods for adjusting the power of an external reader

Disclosed herein are methods and systems for adjusting the power level of an external reader of an electronic device. The external reader transmits power to the electronic device with a radio frequency electromagnetic signal. The electronic device may rectify the radio frequency electromagnetic signal and create a rectified voltage. The rectified voltage may be positively correlated to the power level transmitted by the external device. The rectified power can be used to power a component of the electronic device, such as a component configured to measure either a voltage or power associated with the rectified voltage. The electronic device may communicate the measured voltage or power back to the external reader. Based on the communicated voltage or power, the external reader may adjust its power level of the transmitted power.

BACKGROUND

Some electronic devices are of sufficiently small size that a power supply cannot reasonably accompany the device. In these instances, the electronic device may receive power from an external power source. The external power source may be configured to supply power to the electronic device wirelessly.

SUMMARY

One aspect of the present disclosure provides an apparatus. The apparatus includes an antenna configured to receive electromagnetic radiation to form a supply signal. The antenna is also configured to output a backscatter signal based on the received electromagnetic radiation. The antenna also can adjust an antenna impedance to cause a backscatter of the received electromagnetic radiation. The apparatus also includes a rectifier configured to rectify the supply signal into a supply voltage. Further, the apparatus includes a power unit configured to measure the supply voltage. Additionally, the apparatus may include a measurement unit configured to cause the antenna impedance to communicate the measured supply voltage via the backscatter of received electromagnetic radiation.

Another aspect of the present disclosure provides reader apparatus. The reader apparatus includes an antenna configured to transmit electromagnetic radiation with a power level. The antenna also is configured to receive backscatter electromagnetic radiation and output a voltage-indication signal based on the backscatter electromagnetic radiation. The reader apparatus also includes a control unit. The control unit may be configured to analyze the voltage-indication signal to determine a voltage of a device that caused the backscatter electromagnetic radiation. The control unit may also be configured to determine a voltage requirement for the device. Further, the control unit may also be configured to responsively adjust the power level based on the voltage requirement.

In yet another aspect of the present disclosure, a method is provided. The method includes receiving electromagnetic radiation with an antenna to form a supply signal. The method also includes rectifying the supply signal into a supply voltage. Another part of the method includes measuring the supply voltage with a measurement unit. Additionally, the method includes adjusting an antenna impedance based on the measured supply voltage to cause a backscatter of the received electromagnetic radiation. The backscatter of the received electromagnetic radiation is based on both the received electromagnetic radiation and the antenna impedance.

DETAILED DESCRIPTION

One aspect of the present disclosure provides a method for adjusting the power level of an external reader of an electronic device, such as a contact lens with integrated electronics. The external reader transmits power to the electronic device with a radio frequency electromagnetic signal. The electronic device may rectify the radio frequency electromagnetic signal and create a rectified voltage. The rectified voltage may be positively correlated to the power level transmitted by the external device. This rectified power may be used to power various components of the electronic device. The rectified power can also be used to power a sensor of the electronic device configured to measure either a voltage or power associated with the rectified voltage. The electronic device may communicate the measured voltage or power back to the external reader. Based on the communicated voltage or power, the external reader may adjust its power level of the transmitted power.

Several benefits may be achieved by adjusting the transmitted power level of the external reader. First, the battery of the external reader may be preserved. The external reader may reduce the power level transmitted, thus reducing the amount of battery power used, while still continuing to maintain functionality of the electronic device. Second, the amount of electromagnetic power that is coupled into the body of a person using the electronic device may be minimized. In some embodiments, the electronic device is part of an eye-mountable device. The power level of the external reader may be chosen to minimize the amount of energy that propagates into the eye of a wearer of the eye-mountable device. Third, the power level transmitted may be reduced in order to prevent the power from interfering (e.g., jamming) nearby electronic devices operating with the same wireless frequency and/or technology. Fourth, if the power level from the external device is too high, the external device may have trouble receiving signals from the electric device. The power may be high enough that the signals communicated from the electronic device back to the external reader may be drowned out.

An external reader device or “reader” can radiate radio frequency radiation to power the sensor. The reader may thereby control the operation of the sensing platform by controlling the supply of power to the sensing platform. In some examples, the reader can operate to intermittently interrogate the sensing platform to provide a reading by radiating sufficient radiation to power the sensing platform to obtain a measurement and communicate the result.

The external reader may also include processing logic. The external reader may receive an indication of a voltage from the electric device and compare the voltage to the voltage required for certain functionality of the electronic device. For example, some functionality of the external device may run on 3.4 Volts while other functionality may require 5 Volts for correct operation. Therefore, when the external reader receives an indication of the voltage of the electronic device, it may be able to adjust its transmitted power to increase (or decrease) the voltage of the electronic device.

The sensor of the ophthalmic sensing platform can be configured with, or be part of, a Radio-frequency Identification (RFID) tag. The RFID tag and reader can communicate using an RFID protocol; e.g., an RFID Generation 2 protocol. The RFID tag can be configured to receive radio signals from the reader. In some embodiments, the reader's signals can be used for both communicating with and powering the RFID tag; while in other embodiments, the RFID tag can be a powered device; e.g., be configured with a battery that powers the tag. In embodiments, where a battery powers the tag, the reader's signals may be used to charge the battery. Therefore, the battery may be wirelessly charged in situ.

The reader can communicate with other devices than the RFID tag. As one possible example, the reader can be equipped with a Bluetooth interface as well as with an RFID interface. The reader can communicate with other devices, e.g., a display device, via a Bluetooth or other protocol. In one example, the reader can obtain data from the RFID tag using RFID command(s); e.g., the RFID Generation 2 standard Read command. Upon obtaining the data, the reader can store, process, and/or communicate the data using the Bluetooth interface to another device, such as the display device. Other interfaces for communicating with devices using other communication protocol(s) are possible as well.

As an example, the above-mentioned contact lens can be configured with a sensor that includes an RFID tag. As mentioned above, the sensor can be configured to take measurements while being worn in an eye of a wearer. Upon taking the measurements, the sensor may store data related to the measurements, and subsequently send the data upon request from the reader. The reader, in turn, can store and/or process the received data. For example, the sensor can take current measurements of a supply voltage in the tag. The reader can process the supply voltage data to determine if the supply voltage is large enough to power various components of the tag. The determination may be based on a desired functionality of the tag.

In some embodiments, the supply voltage information can be sent from the reader to a display device. The display device could be, for example, a wearable, laptop, desktop, handheld, or tablet computer, a mobile phone, or a subsystem of such a device. The display device can include a processing system; e.g., a central processing unit (CPU), and a non-transitory computer readable medium configured to store at least program instructions. One example of a wearable computer is a head-mountable display (HMD). The HMD can be a device that is capable of being worn on the head and places a display in front of one or both eyes of the wearer. The display device can store the data received from the reader, perhaps process the data, and generate display(s) based on the received and/or processed data.

In some embodiments, the reader and the display device can be configured with configuration data to perform supply voltage processing. For example, the reader can include configuration data such as current measurement data for various levels of the supply voltage. Based on this configuration data, the reader can determine if the supply voltage is high enough to power various components of the tag. Also, the wearer may provide an input to the display device to indicate a desired functionality of the tag. Based on the desired functionality of the tag, a threshold supply voltage may be needed.

During operation of these embodiments, the RFID tag in an eye of the wearer can generate supply voltage data and send the supply voltage data to the reader. The reader can then process the supply voltage data to compare it with a threshold supply voltage based on a desired functionality of the tag. Then, the display device can be configured to adjust a power level of the signal transmitted from the reader to the tag. In particular embodiments, either the reader or the display device can take supply voltage data as inputs and adjust a power level of the signal transmitted from the reader to the tag as output; i.e., all processing can take place at either the reader or display device.

In some embodiments, the reader can be configured to be worn in proximity to one or more contact lenses configured with sensors worn by a person. For example, the reader can be configured to be part of a pair of eyeglasses, jewelry (e.g., earrings, necklace), headband, head cover such as a hat or cap, earpiece, other clothing (e.g., a scarf), and/or other devices. As such, the reader can provide power and/or receive measurements while proximate to the worn contact lens(es).

In other embodiments, both the display and the reader may be combined into a single unit. For example, a device, such as a mobile phone, may have functionality to act as both the display and the reader to interact with the tag.

Configuring the reader to be frequently worn in proximity to one or more contact lenses enables the lenses to have a reliable external power source and/or storage for sensor data collection, processing of sensor data, and transmission of unprocessed and/or processed sensor data to additional devices; e.g., the above-mentioned display device. Thus, the herein-described reader can provide valuable support functionality, including but not limited to power, communication, and processing resources, to enhance use of contact lenses with embedded sensors, while enabling consequent reduction of support functions on the contact lens. This reduction of support functions on the contact lens may free resources on the contact lens to enable addition of more and/or different sensors and to provide for other functionality on the contact lens.

FIG. 1is a block diagram of a system100that includes an eye-mountable device110in wireless communication with a reader180. The exposed regions of the eye-mountable device110are made of a polymeric material120formed to be contact-mounted to a corneal surface of an eye. A substrate130is embedded in the polymeric material120to provide a mounting surface for a power supply140, a controller150, voltage sensor160, and a communication antenna170. The voltage sensor160may be operated by the controller150or it may operate based on receiving the DC Power141. The power supply140supplies operating voltages to the controller150and/or the voltage sensor160. The antenna170is operated by the controller150to communicate information to and/or from the eye-mountable device110. The antenna170, the controller150, the power supply140, and the voltage sensor160can all be situated on the embedded substrate130. Because the eye-mountable device110includes electronics and is configured to be contact-mounted to an eye, it is also referred to herein as an ophthalmic electronics platform.

To facilitate contact-mounting, the polymeric material120can have a concave surface configured to adhere (“mount”) to a moistened corneal surface (e.g., by capillary forces with a tear film coating the corneal surface). Additionally or alternatively, the eye-mountable device110can be adhered by a vacuum force between the corneal surface and the polymeric material due to the concave curvature. While mounted with the concave surface against the eye, the outward-facing surface of the polymeric material120can have a convex curvature that is formed to not interfere with eye-lid motion while the eye-mountable device110is mounted to the eye. For example, the polymeric material120can be a substantially transparent curved polymeric disk shaped similarly to a contact lens.

The polymeric material120can include one or more biocompatible materials, such as those employed for use in contact lenses or other ophthalmic applications involving direct contact with the corneal surface. The polymeric material120can optionally be formed in part from such biocompatible materials or can include an outer coating with such biocompatible materials. The polymeric material120can include materials configured to moisturize the corneal surface, such as hydrogels and the like. In some embodiments, the polymeric material120can be a deformable (“non-rigid”) material to enhance wearer comfort. In some embodiments, the polymeric material120can be shaped to provide a predetermined, vision-correcting optical power, such as can be provided by a contact lens.

The substrate130includes one or more surfaces suitable for mounting the voltage sensor160, the controller150, the power supply140, and the antenna170. The substrate130can be employed both as a mounting platform for chip-based circuitry (e.g., by flip-chip mounting to connection pads) and/or as a platform for patterning conductive materials (e.g., gold, platinum, palladium, titanium, copper, aluminum, silver, metals, other conductive materials, combinations of these, etc.) to create electrodes, interconnects, connection pads, antennae, etc. In some embodiments, substantially transparent conductive materials (e.g., indium tin oxide) can be patterned on the substrate130to form circuitry, electrodes, etc. For example, the antenna170can be formed by forming a pattern of gold or another conductive material on the substrate130by deposition, photolithography, electroplating, etc. Similarly, interconnects151,157between the controller150and the voltage sensor160, and between the controller150and the antenna170, respectively, can be formed by depositing suitable patterns of conductive materials on the substrate130. A combination of microfabrication techniques including, without limitation, the use of photoresists, masks, deposition techniques, and/or plating techniques can be employed to pattern materials on the substrate130. The substrate130can be a relatively rigid material, such as polyethylene terephthalate (“PET”) or another material configured to structurally support the circuitry and/or chip-based electronics within the polymeric material120. The eye-mountable device110can alternatively be arranged with a group of unconnected substrates rather than a single substrate. For example, the controller150and a voltage sensor160can be mounted to one substrate, while the antenna170is mounted to another substrate and the two can be electrically connected via the interconnects157.

In some embodiments, the voltage sensor160(and the substrate130) can be positioned away from the center of the eye-mountable device110and thereby avoid interference with light transmission to the central, light-sensitive region of the eye. For example, where the eye-mountable device110is shaped as a concave-curved disk, the substrate130can be embedded around the periphery (e.g., near the outer circumference) of the disk. In some embodiments, however, the voltage sensor160(and the substrate130) can be positioned in or near the central region of the eye-mountable device110. Additionally or alternatively, the voltage sensor160and/or substrate130can be substantially transparent to incoming visible light to mitigate interference with light transmission to the eye. Moreover, in some embodiments, the voltage sensor160can include a pixel array (not shown) that emits and/or transmits light to be received by the eye according to display instructions. Thus, the voltage sensor160can optionally be positioned in the center of the eye-mountable device so as to generate perceivable visual cues to a wearer of the eye-mountable device110, such as by displaying information (e.g., characters, symbols, flashing patterns, etc.) on the pixel array.

The substrate130can be ring-shaped with a radial width dimension sufficient to provide a mounting platform for the embedded electronics components. The substrate130can have a thickness sufficiently small to allow the substrate130to be embedded in the polymeric material120without influencing the profile of the eye-mountable device110. The substrate130can have a thickness sufficiently large to provide structural stability suitable for supporting the electronics mounted thereon. For example, the substrate130can be shaped as a ring with a diameter of about 10 millimeters, a radial width of about 1 millimeter (e.g., an outer radius 1 millimeter larger than an inner radius), and a thickness of about 50 micrometers. The substrate130can optionally be aligned with the curvature of the eye-mounting surface of the eye-mountable device110(e.g., convex surface). For example, the substrate130can be shaped along the surface of an imaginary cone between two circular segments that define an inner radius and an outer radius. In such an example, the surface of the substrate130along the surface of the imaginary cone defines an inclined surface that is approximately aligned with the curvature of the eye mounting surface at that radius.

The power supply140is configured to harvest ambient energy to power the controller150and voltage sensor160. For example, a radio-frequency energy-harvesting antenna142can capture energy from incident radio radiation. Additionally or alternatively, solar cell(s)144(“photovoltaic cells”) can capture energy from incoming ultraviolet, visible, and/or infrared radiation. Furthermore, an inertial power scavenging system can be included to capture energy from ambient vibrations. The energy harvesting antenna142can optionally be a dual-purpose antenna that is also used to communicate information to the reader180. That is, the functions of the communication antenna170and the energy harvesting antenna142can be accomplished with the same physical antenna.

A rectifier/regulator146can be used to condition the captured energy to a stable DC supply voltage141that is supplied to the controller150. For example, the energy harvesting antenna142can receive incident radio frequency radiation. Varying electrical signals on the leads of the antenna142are output to the rectifier/regulator146. The rectifier/regulator146rectifies the varying electrical signals to a DC voltage and regulates the rectified DC voltage to a level suitable for operating the controller150. Additionally or alternatively, output voltage from the solar cell(s)144can be regulated to a level suitable for operating the controller150. The rectifier/regulator146can include one or more energy storage devices to mitigate high frequency variations in the ambient energy gathering antenna142and/or solar cell(s)144. For example, one or more energy storage devices (e.g., a capacitor, an inductor, etc.) can be connected in parallel across the outputs of the rectifier146to regulate the DC supply voltage141and configured to function as a low-pass filter.

The controller150is turned on when the DC supply voltage141is provided to the controller150, and the logic in the controller150operates the voltage sensor160and the antenna170. The controller150can include logic circuitry configured to operate the voltage sensor160so as to interact with the antenna170to control the impedance of the antenna170. The impedance of the antenna170may be used to communicate via backscatter radiation. Antenna170and backscatter radiation are discussed further below.

In one example, the controller150includes a sensor interface module152that is configured to interface with the voltage sensor160. The voltage sensor160can be, for example, an electrical sensor configured to provide an output based on an input voltage of the voltage sensor160. A voltage can be applied at the input of the voltage sensor160. The voltage sensor160may responsively create an output based on the input voltage. However, in some instances the input voltage may not be sufficiently high to power the voltage sensor160. When the input voltage is not high enough to power the voltage sensor160, the voltage sensor160may not provide any output. Although the current disclosure generally referrers to voltage sensor160as sensing a voltage, various other electrical sensors may be used in the place of voltage sensor160. For example, a current sensor, a power sensor, or other electrical sensor may be used in the place of the voltage sensor160within the context of the present disclosure.

The controller150can optionally include a display driver module154for operating a pixel array. The pixel array can be an array of separately programmable light transmitting, light reflecting, and/or light emitting pixels arranged in rows and columns. The individual pixel circuits can optionally include liquid crystal technologies, microelectromechanical technologies, emissive diode technologies, etc. to selectively transmit, reflect, and/or emit light according to information from the display driver module154. Such a pixel array can also optionally include more than one color of pixels (e.g., red, green, and blue pixels) to render visual content in color. The display driver module154can include, for example, one or more data lines providing programming information to the separately programmed pixels in the pixel array and one or more addressing lines for setting groups of pixels to receive such programming information. Such a pixel array situated on the eye can also include one or more lenses to direct light from the pixel array to a focal plane perceivable by the eye.

The controller150can also include a communication circuit156for sending and/or receiving information via the antenna170. The communication circuit156can optionally include one or more oscillators, mixers, frequency injectors, etc. to modulate and/or demodulate information on a carrier frequency to be transmitted and/or received by the antenna170. As previously stated, in some examples, the eye-mountable device110is configured to indicate an output from a voltage sensor160by modulating an impedance of the antenna170in a manner that is perceivable by the reader180. For example, the communication circuit156can cause variations in the amplitude, phase, and/or frequency of backscatter radiation from the antenna170, and such variations can be detected by the reader180.

The controller150is connected to the voltage sensor160via interconnects151. For example, where the controller150includes logic elements implemented in an integrated circuit to form the sensor interface module152and/or display driver module154, a patterned conductive material (e.g., gold, platinum, palladium, titanium, copper, aluminum, silver, metals, combinations of these, etc.) can connect a terminal on the chip to the voltage sensor160. Similarly, the controller150is connected to the antenna170via interconnects157.

It is noted that the block diagram shown inFIG. 1is described in connection with functional modules for convenience in description. However, embodiments of the eye-mountable device110can be arranged with one or more of the functional modules (“sub-systems”) implemented in a single chip, integrated circuit, and/or physical component. For example, while the rectifier/regulator146is illustrated in the power supply block140, the rectifier/regulator146can be implemented in a chip that also includes the logic elements of the controller150and/or other features of the embedded electronics in the eye-mountable device110. Thus, the DC supply voltage141that is provided to the controller150from the power supply140can be a supply voltage that is provided to components on a chip by rectifier and/or regulator components located on the same chip. That is, the functional blocks inFIG. 1shown as the power supply block140and controller block150need not be implemented as physically separated modules. Moreover, one or more of the functional modules described inFIG. 1can be implemented by separately packaged chips electrically connected to one another.

Additionally or alternatively, the energy harvesting antenna142and the communication antenna170can be implemented with the same physical antenna. For example, a loop antenna can both harvest incident radiation for power generation and communicate information via backscatter radiation.

The reader180can be configured to be external to the eye; i.e., is not part of the eye-mountable device. Reader180can include one or more antennas188to send and receive wireless signals171to and from the eye-mountable device110. In some embodiments, reader180can communicate using hardware and/or software operating according to one or more standards, such as, but not limited to, a RFID standard, a Bluetooth standard, a Wi-Fi standard, a Zigbee standard, etc.

Reader180can also include a computing system with a processor186in communication with a memory182. Memory182is a non-transitory computer-readable medium that can include, without limitation, magnetic disks, optical disks, organic memory, and/or any other volatile (e.g. RAM) or non-volatile (e.g. ROM) storage system readable by the processor186. The memory182can include a data storage183to store indications of data, such as sensor readings (e.g., from the voltage sensor160), program settings (e.g., to adjust behavior of the eye-mountable device110and/or reader180), etc. The memory182can also include program instructions184for execution by the processor186to cause the reader180to perform processes specified by the instructions184. For example, the program instructions184can cause reader180to provide a user interface that allows for retrieving information communicated from the eye-mountable device110(e.g., sensor outputs from the voltage sensor160). The reader180can also include one or more hardware components for operating the antenna188to send and receive the wireless signals171to and from the eye-mountable device110. For example, oscillators, frequency injectors, encoders, decoders, amplifiers, filters, etc. can drive the antenna188according to instructions from the processor186.

In some embodiments, reader180can be a smart phone, digital assistant, or other portable computing device with wireless connectivity sufficient to provide the wireless communication link171. In other embodiments, reader180can be implemented as an antenna module that can be plugged in to a portable computing device; e.g., in scenarios where the communication link171operates at carrier frequencies not commonly employed in portable computing devices. In even other embodiments discussed below in more detail in the context of at leastFIG. 5, the reader180can be a special-purpose device configured to be worn relatively near a wearer's eye to allow the wireless communication link171to operate with a low power budget. For example, the reader180can be integrated in a piece of jewelry such as a necklace, earring, etc. or integrated in an article of clothing worn near the head, such as a hat, headband, etc.

FIG. 2Ais a bottom view of an example eye-mountable electronic device210(or ophthalmic electronics platform).FIG. 2Bis an aspect view of the example eye-mountable electronic device shown inFIG. 2A. It is noted that relative dimensions inFIGS. 2A and 2Bare not necessarily to scale, but have been rendered for purposes of explanation only in describing the arrangement of the example eye-mountable electronic device210. The eye-mountable device210is formed of a polymeric material220shaped as a curved disk. In some embodiments, eye-mountable device210can include some or all of the above-mentioned aspects of eye-mountable device110. In other embodiments, eye-mountable device110can further include some or all of the herein-mentioned aspects of eye-mountable device210.

The polymeric material220can be a substantially transparent material to allow incident light to be transmitted to the eye while the eye-mountable device210is mounted to the eye. The polymeric material220can be a biocompatible material similar to those employed to form vision correction and/or cosmetic contact lenses in optometry, such as polyethylene terephthalate (“PET”), polymethyl methacrylate (“PMMA”), polyhydroxyethylmethacrylate (“polyHEMA”), silicone hydrogels, combinations of these, etc. The polymeric material220can be formed with one side having a concave surface226suitable to fit over a corneal surface of an eye. The opposite side of the disk can have a convex surface224that does not interfere with eyelid motion while the eye-mountable device210is mounted to the eye. A circular outer side edge228connects the concave surface224and convex surface226.

The eye-mountable device210can have dimensions similar to a vision correction and/or cosmetic contact lenses, such as a diameter of approximately 1 centimeter, and a thickness of about 0.1 to about 0.5 millimeters. However, the diameter and thickness values are provided for explanatory purposes only. In some embodiments, the dimensions of the eye-mountable device210can be selected according to the size and/or shape of the corneal surface of the wearer's eye.

The polymeric material220can be formed with a curved shape in a variety of ways. For example, techniques similar to those employed to form vision-correction contact lenses, such as heat molding, injection molding, spin casting, etc. can be employed to form the polymeric material220. While the eye-mountable device210is mounted in an eye, the convex surface224faces outward to the ambient environment while the concave surface226faces inward, toward the corneal surface. The convex surface224can therefore be considered an outer, top surface of the eye-mountable device210whereas the concave surface226can be considered an inner, bottom surface. The “bottom” view shown inFIG. 2Ais facing the concave surface226. From the bottom view shown inFIG. 2A, the outer periphery222, near the outer circumference of the curved disk is curved to extend out of the page, whereas the central region221, near the center of the disk is curved to extend into the page.

A substrate230is embedded in the polymeric material220. The substrate230can be embedded to be situated along the outer periphery222of the polymeric material220, away from the central region221. The substrate230does not interfere with vision because it is too close to the eye to be in focus and is positioned away from the central region221where incident light is transmitted to the eye-sensing portions of the eye. Moreover, the substrate230can be formed of a transparent material to further mitigate effects on visual perception.

The substrate230can be shaped as a flat, circular ring (e.g., a disk with a centered hole). The flat surface of the substrate230(e.g., along the radial width) is a platform for mounting electronics such as chips (e.g., via flip-chip mounting) and for patterning conductive materials (e.g., via microfabrication techniques such as photolithography, deposition, plating, etc.) to form electrodes, antenna(e), and/or interconnections. The substrate230and the polymeric material220can be approximately cylindrically symmetric about a common central axis. The substrate230can have, for example, a diameter of about 10 millimeters, a radial width of about 1 millimeter (e.g., an outer radius 1 millimeter greater than an inner radius), and a thickness of about 50 micrometers. However, these dimensions are provided for example purposes only, and in no way limit the present disclosure. The substrate230can be implemented in a variety of different form factors, similar to the discussion of the substrate130in connection withFIG. 1above.

A loop antenna270, controller250, and voltage sensor260are disposed on the embedded substrate230. The controller250can be a chip including logic elements configured to operate the voltage sensor260and the loop antenna270. The controller250is electrically connected to the loop antenna270by interconnects257also situated on the substrate230. Similarly, the controller250is electrically connected to the voltage sensor260by an interconnect251. The interconnects251,257, the loop antenna270, and any conductive electrodes (e.g., for a voltage sensor, etc.) can be formed from conductive materials patterned on the substrate230by a process for precisely patterning such materials, such as deposition, photolithography, etc. The conductive materials patterned on the substrate230can be, for example, gold, platinum, palladium, titanium, carbon, aluminum, copper, silver, silver-chloride, conductors formed from noble materials, metals, combinations of these, etc.

As shown inFIG. 2A, which is a view facing the convex surface224of the eye-mountable device210, voltage sensor260is mounted to a side of the substrate230facing the convex surface224. In some embodiments, some electronic components can be mounted on one side of the substrate230, while other electronic components are mounted to the opposing side, and connections between the two can be made through conductive materials passing through the substrate230.

The loop antenna270is a layer of conductive material patterned along the flat surface of the substrate to form a flat conductive ring. In some instances, the loop antenna270can be formed without making a complete loop. For instances, the loop antenna can have a cutout to allow room for the controller250and voltage sensor260, as illustrated inFIG. 2A. However, the loop antenna270can also be arranged as a continuous strip of conductive material that wraps entirely around the flat surface of the substrate230one or more times. For example, a strip of conductive material with multiple windings can be patterned on the side of the substrate230opposite the controller250and voltage sensor260. Interconnects between the ends of such a wound antenna (e.g., the antenna leads) can then be passed through the substrate230to the controller250.

FIG. 2Cis a side cross-section view of the example eye-mountable electronic device210while mounted to a corneal surface22of an eye10.FIG. 2Dis a close-in side cross-section view enhanced to show the eye-mountable device210. It is noted that relative dimensions inFIGS. 2C and 2Dare not necessarily to scale, but have been rendered for purposes of explanation only in describing the arrangement of the example eye-mountable electronic device210. For example, the total thickness of the eye-mountable device can be about 200 micrometers, while the thickness of the tear film layers can each be about 10 micrometers, although this ratio may not be reflected in the drawings. Some aspects are exaggerated to allow for illustration and facilitate explanation.

The eye10includes a cornea20that is covered by bringing the upper eyelid30and lower eyelid32together over the top of the eye10. Incident light is received by the eye10through the cornea20, where light is optically directed to light sensing elements of the eye10(e.g., rods and cones, etc.) to stimulate visual perception. The motion of the eyelids30,32distributes a tear film across the exposed corneal surface22of the eye10. The tear film is an aqueous solution secreted by the lacrimal gland to protect and lubricate the eye10. When the eye-mountable device210is mounted in the eye10, a tear film coats both the concave and convex surfaces224,226with an inner layer (along the concave surface226) and an outer layer (along the convex layer224). The tear film layers can be about 10 micrometers in thickness and together account for about 10 microliters.

The tear film layers are distributed across the corneal surface22and/or the convex surface224by motion of the eyelids30,32. For example, the eyelids30,32raise and lower, respectively, to spread a small volume of tear film across the corneal surface22and/or the convex surface224of the eye-mountable device210. The tear film layer on the corneal surface22also facilitates mounting the eye-mountable device210by capillary forces between the concave surface226and the corneal surface22. In some embodiments, the eye-mountable device210can also be held over the eye in part by vacuum forces against corneal surface22due to the concave curvature of the eye-facing concave surface226.

As shown in the cross-sectional views inFIGS. 2C and 2D, the substrate230can be inclined such that the flat mounting surfaces of the substrate230are approximately parallel to the adjacent portion of the convex surface224. As described above, the substrate230is a flattened ring with an inward-facing surface232(facing concave surface226of the polymeric material220) and an outward-facing surface234(facing convex surface224). The substrate230can have electronic components and/or patterned conductive materials mounted to either or both mounting surfaces232,234. As shown inFIG. 2D, the voltage sensor260, controller250, and conductive interconnect251may be mounted on the outward-facing surface234. However, in other embodiments, the various components may also be mounted on the inward-facing surface.

The polymer layer defining the anterior side may be greater than 50 micrometers thick, whereas the polymer layer defining the posterior side may be less than 150 micrometers. Thus, voltage sensor260may be at least 50 micrometers away from the convex surface224and may be a greater distance away from the concave surface226. However, in other examples, the voltage sensor260may be mounted on the inward-facing surface232of the substrate230such that the voltage sensor260are facing concave surface226. The voltage sensor260could also be positioned closer to the concave surface226than the convex surface224.

FIG. 3is a functional block diagram of a system300for adjusting the power of an external reader. The system300includes an eye-mountable device210with embedded electronic components in communication with and powered by reader180. Reader180can also be configured to communicate with a display device (the display device may or may not be integrated with the reader180as UI348). Reader180and eye-mountable device210can communicate according to one communication protocol or standard, shown inFIG. 3as RF Power341. In one particular embodiment, the protocol used for RF Power341and Backscatter communication343is an RFID protocol. The eye-mountable device210includes an antenna312for capturing radio frequency (RF) power341from the reader180. The antenna312may also create backscatter communication343.

The eye-mountable device210includes rectifier314, energy storage316(that may output unregulated voltage317), and regulator318for generating regulated supply voltages330,332to operate the embedded electronics. The eye-mountable device210includes a voltage sensor321that may have a sensor interface320. The eye-mountable device210includes hardware logic324for communicating results from the sensor321to the reader180by modulating the impedance of the antenna312. An impedance modulator325(shown symbolically as a switch inFIG. 3) can be used to modulate the antenna impedance according to instructions from the hardware logic324. Similar to the eye-mountable device110discussed above in connection withFIG. 1, the eye-mountable device210can include a mounting substrate embedded within a polymeric material configured to be mounted to an eye.

With reference toFIG. 3, in various embodiments, the voltage sensor321measures either the unregulated voltage317or the regulated supply voltage332. In various embodiments, the voltage measured by the voltage sensor321may come from different sources. As shown inFIG. 3, the regulator318may provide the regulated supply voltage332and the energy storage316may provide unregulated voltage317. However, in other embodiments, only one of the regulated supply voltage332and the unregulated voltage317may be provided to the voltage sensor321. In additional embodiments, the regulated supply voltage332provided to the voltage sensor321may be the same regulated supply voltage330that supplies power to the hardware logic324. The connections shown inFIG. 3are one example of possible configurations for the voltage sensor321. The sensor interface320may be configured as a part of the voltage sensor321itself. For example, the sensor interface320may convert the output of the voltage sensor321into a format that in understandable by the hardware logic324.

In other embodiments, the sensor interface320can contain an electrical sensor other than voltage sensor321. For example, a current sensor, a power sensor, or other electrical sensor may be used in the place of the voltage sensor321within the context of the present disclosure. The connections to the sensor interface320may change depending on the specific type of sensor that forms a portion of sensor interface320. For example, the sensor unit320contains a parallel electrical connection to the hardware logic324. A current sensor may be placed in a series electrical connection with one of the hardware logic324, voltage regulator318, or other component.

The rectifier314, energy storage316, and voltage regulator318operate to harvest energy from received RF power341. RF power341causes radio frequency electrical signals on leads of the antenna312. The rectifier314is connected to the antenna leads and converts the radio frequency electrical signals to a DC voltage. The energy storage316(e.g., capacitor) is connected across the output of the rectifier314to filter out high frequency components of the DC voltage. The regulator318receives the filtered DC voltage (e.g. unregulated voltage317) and outputs both a regulated supply voltage330to operate the hardware logic324and a regulated supply voltage332to operate the voltage sensor321of the sensor interface320. For example, the supply voltage can be equivalent to the voltage of the energy storage316. In another example, the supply voltage can be equivalent to the voltage of the rectified DC voltage from the rectifier314. Additionally, the regulated supply voltage330can be a voltage suitable for driving digital logic circuitry, such as approximately 1.2 volts, approximately 3 volts, etc. The voltage needed as the regulated supply voltage330may change depending on a functionality requirement of the logic324(or a voltage requirement of other components of the eye-mountable device210). Reception of the RF power341from the reader180(or another source, such as ambient radiation, etc.) causes the regulated supply voltages330,332to be supplied to the sensor320and hardware logic324. While powered, the sensor320and hardware logic324are configured to generate and measure a voltage (such as either unregulated voltage317or regulated supply voltages332) and communicate the results.

The sensor results can be communicated back to the reader180via backscatter radiation343from the antenna312. The hardware logic324receives the supply voltage from the sensor interface320(or the voltage sensor321itself) and modulates (325) the impedance of the antenna312in accordance with the supply voltage measured by the sensor320. The antenna impedance and/or change in antenna impedance are detected by the reader180via the backscatter signal343.

Reader180can include an antenna and RF front end342and logic components344to communicate using a radio protocol, decode the information indicated by the backscatter signal343, provide digital inputs to a processing system346and receive inputs and/or provide outputs via user interface348. The radio protocol can be, for example, an RFID protocol. In some embodiments, part or all of eye-mountable device210can be configured to perform some or all features of an RFID tag. For example, as shown inFIG. 3, some or all of the components shown as tag370of eye-mountable device210can perform some or all features of an RFID tag; e.g., antenna312, rectifier314, energy storage316, voltage regulator318, hardware logic324, etc.

In some embodiments, one or more of the features shown as separate functional blocks can be implemented (“packaged”) on a single chip. For example, the eye-mountable device210can be implemented with the rectifier314, energy storage316, voltage regulator318, sensor interface320, and the hardware logic324packaged together in a single chip or controller module. Such a controller can have interconnects (“leads”) connected to the loop antenna312and the sensor electrodes322,323. Such a controller operates to harvest energy received at the loop antenna312, measure the supply voltage created by the harvested energy, and indicate the measured supply voltage via the antenna312(e.g., through the backscatter communication343).

A processing system, such as, but not limited to, processing system346or processing system356, can include one or more processors and one or more storage components. Example processor(s) include, but are not limited to, CPUs, Graphics Processing Units (GPUs), digital signal processors (DSPs), application specific integrated circuits (ASICs). Example storage component(s) include, but are not limited to volatile and/or non-volatile storage components, e.g., optical, magnetic, organic or other memory, disc storage; Random Access Memory (RAM), Read-Only Memory (ROM), flash memory, optical memory unit, and disc memory. The storage component(s) can be configured to store software and data; e.g., computer-readable instructions configured, when executed by a processor of the processing system, to cause the processing system to carry out functions such as but not limited to the herein-described functions of reader180, eye-mountable device210, and/or display device350.

The reader180can associate the backscatter signal343with the sensor result (e.g., via the processing system346according to a pre-programmed relationship associating impedance of the antenna312with output from the sensor320). The processing system346can then store the indicated sensor results (e.g., induced supply voltage) in a local memory and/or an external memory (e.g., by communicating with the external memory either on display device350or through a network).

User interface348of reader180can include an indicator, such as but not limited to one or more light-emitting diodes (LEDs) and/or speakers, that can indicate that reader180is operating and provide some information about its status. For example, reader180can be configured with an LED that displays one color (e.g., green) when operating normally and another color (e.g., red) when operating abnormally. In other embodiments, the LED(s) can change display when processing and/or communicating data in comparison to when idle (e.g., periodically turn on and off while processing data, constantly stay on or constantly stay off while idle). The reader180may also provide an audio output based on the voltage sensor data.

In some embodiments, one or more of the LED(s) of user interface348can indicate a status of sensor data; e.g., not display when sensor data are either within normal range(s) or unavailable, display in a first color when sensor data are either outside normal range(s) but not extremely high or low, and display a second color when the sensor data are extremely high and/or low. For example, if the voltage sensor data is unavailable, it may indicate that the RF Power341is too low to induce a voltage in the eye-mountable device210to power the voltage sensor321. In another embodiment, the voltage sensor data may indicate the voltage is too low based on the RF Power341being too low to induce a voltage to power a component (or a function) of the eye-mountable device210. In yet another embodiment, the voltage sensor data may indicate the voltage is too high based on the RF Power341being high enough to induce a voltage power a component (or a function) of the eye-mountable device210, but the voltage is sufficiently higher than needed. In some embodiments, the processing system346may responsively adjust the RF Power341based on the voltage sensor data.

In some embodiments, reader180can communicate with devices in addition to eye-mountable device210/tag370. For example, the reader180may also function as a cellular phone or other mobile device.

FIG. 4is a block diagram of a system400with eye-mountable device210operated by a reader180to obtain a series of supply voltage measurements over time. An electrical sensor; e.g., an embodiment of sensor321, can be included with eye-mountable device210. As shown inFIG. 4, eye-mountable device210is configured to be contact-mounted over a corneal surface of an eye10. The ophthalmic electrical sensor can be operated to be transitioned into an active measurement mode in response to receiving a signal from the reader180.

The reader180includes a processing system346, configured with memory414.

The processing system412can be a computing system that executes computer-readable instruction stored in the memory414to cause the reader180/system400to obtain a time series of measurements by intermittently transmitting a measurement signal to eye-mountable device210. In response to the measurement signal, one or more sensors of eye-mountable device210; e.g., electrical sensor430, can take measurement(s), obtain results of the measurement(s), and communicate the results to reader180via backscatter422. As discussed above regardingFIG. 3, reader180can provide RF power, such as RF power420, to be harvested by the eye-mountable device210. For example, impedance of an antenna of eye-mountable device210can be modulated in accordance with the sensor result such that the backscatter radiation422indicates the sensor results. Reader180can also use memory414to store indications of supply voltage measurements communicated by the voltage sensor430. The reader180can thus be operated to intermittently power the electrical sensor430so as to obtain a time series of supply voltage measurements.

FIG. 5shows an example wearer500wearing two eye-mountable devices210a,210b, a band522, earrings524a,524b, and a necklace526. As discussed above at least in the context ofFIGS. 3, 4A, and 4B, each eye-mountable device210a,210bcan be configured with sensor(s) to measure at least the supply voltage induced in the respective lens.

The functionality of band522can be performed by a structure of another device, e.g., an eye-glass frame, a head-mountable computer frame, a cap, a hat, part of a hat or cap (e.g., a hat band or bill of a baseball cap), a headphone headband, etc., or by a separate band; e.g., a head band, a scarf or bandanna worn as a head band. For examples, band522can be supported by ear(s), nose, hair, skin, and/or a head of wearer500, and perhaps by external devices e.g., stick pins, bobby pins, headband elastics, snaps. Other and different support(s) for band522are possible as well.

One or more of band522, earrings524a,524b, and necklace526can be configured to include one or more readers; e.g., the above-mentioned reader180.FIG. 5shows three example positions180a,180b, and180cfor readers in band522. For example, if only eye-mountable device210ahas a sensor, then a reader, such as reader180, can be mounted in example positions180aand/or180bto send commands and power to eye-mountable device210a. Similarly, to power and communicate with a sensor in eye-mountable device210b, a reader mounted in band522, such as reader180, can be mounted in example positions180band/or180c.

Each of or both earrings524a,524bcan be configured with respective readers180d,180efor communicating with and power sensors in respective eye-mountable devices210a,210b. Necklace526can be configured with one or more readers180f,180g,180hfor communicating with and power sensors in respective eye-mountable device210a,210b. Other embodiments are possible as well; e.g., readers in positions180a-180cor near those positions can be configured as part of a hat, headband, scarf, jewelry (e.g., a brooch), glasses, head mounted device, and/or other apparatus.

In some embodiments, a reader can power a sensor in eye-mountable device210using a low-power transmission; e.g., a transmission of 1 watt or less of power. In these embodiments, the reader can be within a predetermined distance; e.g., 1 foot, 40 cm, of eye-mountable device210a,210bto power the sensor.

In other scenarios, the reader, tag, display device, and/or other device(s) can communicate using different and/or additional protocols; e.g., an IEEE 802.11 protocol (“Wi-Fi”), an IEEE 802.15 protocol (“Zigbee”), a Local Area Network (LAN) protocol, a Wireless Wide Area Network (WWAN) protocol such as but not limited to a 2G protocol (e.g., CDMA, TDMA, GSM), a 3G protocol (e.g., CDMA-2000, UMTS), a 4G protocol (e.g., LTE, WiMAX), a wired protocol (e.g., USB, a wired IEEE 802 protocol, RS-232, DTMF, dial pulse). Many other examples of protocol(s) and combination(s) of protocols can be used as well.

Although scenario600in shown in a linear order, the blocks may also be performed in a different order. Additionally, in some embodiments, at least one block of scenario600may be performed in parallel to another block of scenario600.

Scenario600begins with reader180sending communication to the eye-mountable device (EMD)210with a transmit RF Power620. The transmitted RF Power620may be a radio signal with a defined radio power. In some embodiments, the radio power may be transmitted as a continuous wave (CW) radio signal or the radio power may be transmitted as a pulse-modulated radio signal. In other embodiments, the RF Power620transmission may take a form other than a CW or pulse-modulated radio signal. In some embodiments, the communication may be an initialization of the eye-mountable device210. However, in other embodiments, the communication may be the normal operation of the eye-mountable device210.

When the EMD210received the RF power620, it converts the RF power620into a supply voltage. The supply voltage is used to power various components within the EMD210. The EMD210may also be configured to measure the supply voltage created in the EMD210. The EMD210may include an electrical component configured to measure the supply voltage induced in the EMD210from the RF power620. Additionally, the EMD210may be configured to create a backscatter signal based on the measured supply voltage622.

After transmitting RF Power620to an EMD210, the reader180may responsively receive a Supply Voltage Indication624communicated from the EMD210. The EMD may communicate the Supply Voltage Indication624through backscatter radiation of the RF Power620. The backscatter radiation may be created by a modulation of an impedance of an antenna of the EMD210. The EMD210may be configured to modulate the antenna impedance to create a signal to communicate a supply voltage induced in the EMD210by RF Power620.

Once the Reader180receives the Supply Voltage Indication624, it may Analyze the Voltage Indication626. When the Reader180Analyzes the Voltage Indication626, it may determine a supply voltage that was induced in the EMD210by the RF power620. In some embodiments, Analyzing the Voltage Indication626may determine that a signal received as Supply Voltage Indication624does not actually contain an indication of supply voltage. In this instance, the lack of an indication of a supply voltage may indicate to the Reader180that the there is an error in the EMD210.

Once the Reader180Analyzes the Voltage Indication626, it may responsively Determine a Voltage Requirement628. The Reader180may Determine a Voltage Requirement628. The Reader180may determine a voltage requirement in several ways. First, the Reader may determine a desired function for the EMD210. Each desired function may have an associated voltage requirement. The Reader180may compare the voltage requirement for the desired function of the EMD210(or, in an instance where the EMD210performs multiple functions, the highest voltage requirement needed for any function). Once the Reader180Determines a Voltage Requirement628, the Reader180may compare the voltage requirement with the voltage indication to determine a difference between the Determined Voltage Requirement626and the Voltage Indication626. In other embodiments, the Reader180may not have been able to determine an inducted voltage in the EMD210when Analyzing the Voltage Indication626. In this embodiment, the Reader180may determine that the voltage induced in the EMD210is too low to power the voltage sensor.

Once the reader has Determined Voltage Requirement628(or determined the induced voltage is too low), the reader may transmit to the EMD120with an Adjusted RF Power630. If the Determined Voltage Requirement628is greater than the induced voltage determined by Determined Voltage Requirement628, then the Adjusted RF Power628will be increased compared to the RF Power620. If the Determined Voltage Requirement628is less than the induced voltage determined by Determined Voltage Requirement628, then the Adjusted RF Power630may be decreased compared to the RF Power620. The Adjusted RF Power630does not have to be decreased in order to power various components of the EMD210(as the voltage is already sufficiently high), but the Adjusted RF Power630may be lowered to both conserve power of the Reader180and reduce the amount of RF Power coupled into the body of the person wearing the EMD210. If the Reader180determines that the voltage induced in the EMD210is too low to power the voltage sensor, the Reader180may increase the RF Power when transmitting the Adjusted RF Power630. Scenario600may be repeated after the RF Power is adjusted. Other examples of scenario600are possible as well.

FIG. 7is a flow chart of an example method700. Method700can be carried out by a device, such as a tag in an eye-mountable device, or a device that includes a processor, such the hardware logic324, the hardware logic may include a computer readable medium storing machine-readable instructions, where the machine-readable instructions, when executed by a processing component of the device, are configured to cause the device to carry out some or all of the techniques described herein as method700.

Method700can begin at block710. At block710, the tag can receive RF (i.e. electromagnetic) power, such as discussed above in the context of at leastFIG. 6. An antenna in the tag may receive the RF power and output an RF signal (as a voltage). The RF signal may be proportional to the received RF power. The tag can be part of an eye-mountable device; e.g., tag370of eye-mountable device210, such as discussed above in more detail in the context of at leastFIG. 3. In some embodiments, the reader can be within a predetermined distance from the tag when transmitting RF power to the tag, such as discussed above in the context of at leastFIG. 5. In other embodiments, the reader can be part of an HMD, such as discussed above in the context of at leastFIG. 5.

At block720, the tag can rectify the RF signal output from the antenna. By rectifying the supply signal, a direct current (DC) supply voltage may be created. Because the supply signal may be a conversion of the propagating RF power to a guided electric RF signal, it may have alternating current properties. For example, the amplitude of the supply signal may vary from a positive voltage to a negative voltage. After rectification, the supply voltage does not have an amplitude that swings from positive to negative. Therefore the supply voltage may be considered an unregulated DC supply voltage.

Additionally, the rectified supply voltage may also be applied across a capacitor or other electrical storage component. The capacitor (or storage component) may perform at least one of two functions. First, the capacitor may store some electrical energy. This electrical energy may be used to power components of the tag if the RF power is no longer applied to the antenna of the tag. Second, the capacitor may also provide some smoothing (e.g. low-pass filtering) of the rectified voltage. This smoothing may allow a more consistent supply voltage to be supplied to the various components of the tag.

At block730, the tag may measure the supply voltage with a measurement unit, such as a voltage sensor. The voltage sensor may be configured to use both the supply power to power itself, as well as measure the voltage of the supply voltage. In other embodiments, the tag can contain an electrical sensor other than a voltage sensor. For example, a current sensor, a power sensor, or other electrical sensor may be used in the place of the voltage sensor within the context of the present disclosure. If the electronic unit has a sensor other than a voltage sensor, a different electrical property of the supply voltage may be measured.

In some embodiments, the supply voltage measured by the voltage sensor is an unregulated voltage. The unregulated voltage may be provided by the output of the capacitor (or other energy storage device). In other embodiments, the supply voltage the voltage sensor may measure is a regulated voltage. The regulated voltage may be a voltage that comes out of a regulator component. A regulated voltage may have a more consistent and stable voltage than the unregulated voltage. Additionally, regulated voltage may be used to supply power to various components of the device.

At block740, the tag may adjust an antenna impedance based on the measured supply voltage. The antenna impedance may be adjusted in a way to cause a backscatter signal of the RF power. The backscatter signal may communicate the measured voltage back to a reader device. Therefore, through the impedance adjustment, the tag may communicate the measured supply voltage back to the reader.

With respect to any or all of the ladder diagrams, scenarios, and flow charts in the figures and as discussed herein, each block and/or communication may represent a processing of information and/or a transmission of information in accordance with example embodiments. Alternative embodiments are included within the scope of these example embodiments. In these alternative embodiments, for example, functions described as blocks, transmissions, communications, requests, responses, and/or messages may be executed out of order from that shown or discussed, including substantially concurrent or in reverse order, depending on the functionality involved. Further, more or fewer blocks and/or functions may be used with any of the ladder diagrams, scenarios, and flow charts discussed herein, and these ladder diagrams, scenarios, and flow charts may be combined with one another, in part or in whole.

It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein. While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art.

Example methods and systems are described above. It should be understood that the words “example” and “exemplary” are used herein to mean “serving as an example, instance, or illustration.” Any embodiment or feature described herein as being an “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or features. Reference is made herein to the accompanying figures, which form a part thereof. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.