Selective fingerprint sensor activation

Certain aspects of the present disclosure provide techniques for selectively activating a fingerprint sensor in an electronic device. A method that may be performed by the electronic device includes detecting a finger hover above the display module, activating the fingerprint sensor based, at least in part, on the detected finger hover, and providing, in response to detecting the finger hover, feedback information to assist in scanning the finger using the fingerprint sensor.

BACKGROUND

Field of the Disclosure

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for selectively activating a fingerprint sensor in an electronic device.

Description of Related Art

Electronic devices utilizing a touchscreen are prevalent in today's technology and may include devices such as a smartphone, a smartwatch, or a tablet computer. A touchscreen can include an electronic visual display that a user can control through simple or multi-touch gestures by touching the screen, for example with a finger. The user can use the touchscreen to react to what is displayed and to control how it is displayed (for example, by zooming the text size). The touchscreen enables the user to interact directly with what is displayed, rather than using a mouse, touchpad, or any other intermediate device (other than a stylus, which is optional for most modern touchscreens).

Such electronic devices may also include one or more sensors or feedback devices, configured to aid the user's experience and provide security for the electronic device. However, such sensor require power to operate. Accordingly, if these sensors are always powered on, these sensor will reduce battery life of the electronic device and waste other resources. Thus, there is a need to improve control of such sensors such that they are able to function according to their purpose without wasting power.

SUMMARY

Certain aspects of the subject matter described in this disclosure can be implemented in a method for activating a fingerprint sensor in a device comprising a display module. The method generally includes detecting a finger hover above the display module, activating the fingerprint sensor based, at least in part, on the detected finger hover, and providing, in response to detecting the finger hover, feedback information to assist in scanning the finger using the fingerprint sensor.

Certain aspects of the subject matter described in this disclosure can be implemented in an apparatus for activating a fingerprint sensor in a device comprising a display module. The apparatus generally includes at least one processor configured to detect a finger hover above the display module, activate the fingerprint sensor based, at least in part, on the detected finger hover, and provide, in response to detecting the finger hover, feedback information to assist in scanning the finger using the fingerprint sensor. The apparatus also includes a memory coupled with the at least one processor.

Certain aspects of the subject matter described in this disclosure can be implemented in an apparatus for activating a fingerprint sensor in a device comprising a display module. The apparatus generally includes means for detecting a finger hover above the display module, means for activating the fingerprint sensor based, at least in part, on the detected finger hover, and means for providing, in response to detecting the finger hover, feedback information to assist in scanning the finger using the fingerprint sensor.

Certain aspects of the subject matter described in this disclosure can be implemented in a non-transitory computer-readable medium for activating a fingerprint sensor in a device comprising a display module. The non-transitory computer-readable medium generally includes instructions that, when executed by at least one processor, cause the at least one processor to detect a finger hover above the display module, activate the fingerprint sensor based, at least in part, on the detected finger hover, and provide, in response to detecting the finger hover, feedback information to assist in scanning the finger using the fingerprint sensor.

Certain aspects of the subject matter described in this disclosure can be implemented in an apparatus configured to beamform ultrasonic pressure waves. The apparatus generally includes a display module comprising a first plurality of layers and a pressure wave module configured for beamforming ultrasonic pressure waves through the display module. In some cases, the pressure wave module comprises a second plurality of layers, which may comprise at least a copolymer layer, a conductive layer, a die attached film (DAF) layer, and a thin film transistor (TFT) glass layer. Additionally, in some cases, an order of the second plurality of layers in the pressure wave module depends on an acoustic resonance value associated with the display module.

Certain aspects of the subject matter described in this disclosure can be implemented in a method for operating an apparatus configured to beamform ultrasonic pressure waves. The method generally includes emitting, via a pressure wave module of the apparatus, beamformed ultrasonic pressure waves through a display module of the apparatus. In some cases, the display module comprises a first plurality of layers and the pressure wave module comprises a second plurality of layers. Additionally, in some cases, the second plurality of layers comprises at least a copolymer layer, a conductive layer, a die attached film (DAF) layer, and a thin film transistor (TFT) glass layer. Additionally, in some cases, an order of the second plurality of layers in the pressure wave module depends on an acoustic resonance value associated with the display module. In some cases, the method may also include receiving, via the pressure wave module, at least one response pressure wave in response to the beamformed ultrasonic pressure waves and detecting a finger hover above the display module based on the at least one response pressure wave.

Certain aspects of the subject matter described in this disclosure can be implemented in an apparatus for beamforming ultrasonic pressure waves. The apparatus generally includes at least one processor configured to control a pressure wave module of the apparatus to emit beamformed ultrasonic pressure waves through a display module of the apparatus. In some cases, the display module comprises a first plurality of layers and the pressure wave module comprises a second plurality of layers. Additionally, in some cases, the second plurality of layers comprises at least a copolymer layer, a conductive layer, a die attached film (DAF) layer, and a thin film transistor (TFT) glass layer. Additionally, in some cases, an order of the second plurality of layers in the pressure wave module depends on an acoustic resonance value associated with the display module. In some cases, the at least one processor may further be configured to receive at least one response pressure wave in response to the beamformed ultrasonic pressure waves and detect a finger hover above the display module based on the at least one response pressure wave. Additionally, the apparatus may also include a memory coupled with the at least one processor.

Certain aspects of the subject matter described in this disclosure can be implemented in an apparatus for beamforming ultrasonic pressure waves. The apparatus generally includes a display module comprising a first plurality of layers and a pressure wave module configured for beamforming ultrasonic pressure waves through the display module. The pressure wave module may be configured to generate ultrasonic pressure waves at a frequency. The apparatus may also include an adhesive layer coupling the pressure wave module with the display module. In some cases, a thickness of the adhesive layer is configured to be one of a half-wavelength of the frequency or a quarter-wavelength of the frequency. The apparatus may also include a spacer layer disposed between the display module and the pressure wave module. The spacer layer may affect a spatial resolution associated with a response signal received by the pressure wave module and may be disposed between the adhesive layer and pressure wave module. In some cases, the pressure wave module comprises a second plurality of layers, which may comprise at least a copolymer layer, a conductive layer, a die attached film (DAF) layer, and a thin film transistor (TFT) glass layer. Additionally, in some cases, an order of the second plurality of layers in the pressure wave module depends on an acoustic resonance value associated with the display module. Further, in some cases, the order comprises the TFT glass layer being disposed below a bottom layer of the first plurality of layers of the display module, the copolymer layer being disposed below the TFT glass layer, the conductive layer being disposed below the copolymer layer, and the DAF layer being disposed below the conductive layer.

DETAILED DESCRIPTION

Certain aspects of the present disclosure provide methods and apparatus for activating a fingerprint sensor in a device comprising a display module. For example, in some cases, a finger hover may be detected above the display module. In response, at least a portion of the fingerprint sensor may be activated based on the detected finger hover. Additionally, in some cases, feedback may be provided to assist in scanning the finger using the fingerprint sensor. In some cases, the finger hover may be detected by beamforming ultrasonic pressure waves through the display module. Accordingly, aspects of the present disclosure also provide methods and apparatus for beamforming ultrasonic pressure waves.

As noted above, electronic devices utilizing a touchscreen are prevalent in today's technology. Such electronic devices may include one or more components for displaying information, providing feedback, and providing security for the electronic device. One such component may include, for example, a fingerprint sensor, which may comprise one or more components configured to capture an image of a fingerprint pattern. The fingerprint pattern may be used identify the user and provide access to the electronic device.

In recent years, various electronic fingerprint scanning systems have been developed utilizing optical, capacitance, direct pressure, thermal and ultrasonic methods. Techniques based on ultrasound have proven to be highly accurate, being insulated from the effects of grease, dirt, paint, ink and other image contaminants. In an ultrasonic system, as explained below, a piezoelectric transducer may be used to send an ultrasonic wave through an ultrasound transmitting media, which may be used to capture an image of the fingerprint pattern, as explained below.

FIG. 1is a perspective view of one such electronic device100. As illustrated, the electronic device100may include a display module102, a fingerprint sensor104, a controller module106.

The display module102may generally include a first plurality of layers and may be used to display information and receive input from a user. The first plurality of layers may comprise one or more of a cover glass layer, a first optical clear adhesive (OCA) layer, a polarizer layer, a back plate pressure-sensitive-adhesive layer (BPSA), a touch sensor layer, a second OCA layer, and a display panel.

The fingerprint sensor104may be disposed below the display module102and may include a plurality of transducer devices (e.g., as shown inFIG. 4) configured to emit pressure waves (e.g., sound waves) to scan a fingerprint of a user and provide access to the electronic device100, as explained below. In some cases, the fingerprint sensor104may include a pressure wave module (e.g., pressure wave module401, illustrated inFIG. 4) that includes a second plurality of layers, such as a copolymer layer, a conductive layer (e.g., silver (Ag) ink), a dielectric protection layer (e.g., a die attached film (DAF) layer), and a thin film transistor (TFT) glass layer.

In pressure-wave-based fingerprint scanners, a controller module106may control the plurality of transducer devices to emit pressure wave pulses. At each material interface encountered by the pulse, a portion of the pulse may be reflected. For example, an interface between a surface of a screen and skin or the interface between air and skin may each reflect a portion of the pulse. The fraction of ultrasound reflected is a function of differences in impedance between the two materials comprising the interface. The fraction of ultrasound reflected can be calculated by the equation, R=((Z1−Z2)/(Z1+Z2))2, where R is the fraction of sound reflected, Z1is the acoustic impedance of a first material and Z2is the acoustic impedance of a second material. Acoustic impedance is a measure of a material's resistance to the propagation of sound. Acoustic impedance, Z, may be defined as Z=r·c, where r is the density of the material, and c is the longitudinal propagation velocity of ultrasound in the material. The larger the change in acoustic impedance, the larger the fraction reflected.

The reflected wave pulses may be detected by a detector in the fingerprint sensor104. The elapsed time during which the pulse traveled from the ultrasound pulse emitter to the interface (e.g., the skin of a user) and back may be determined. The elapsed time may be used to determine the distances traveled by the pulse and its reflected wave pulses. By knowing the distance traveled, the position and features of an interface may be determined. For example, by emitting a plurality of wave pulses and receiving their corresponding reflections, minute features of an object, such as fingerprints of a finger, may be determined.

Current fingerprint sensors in electronic devices, such as mobile devices, are very small in size and require precise finger placement on the sensor to successfully match a fingerprint and unlock the device. One way to address this issue is to use a larger fingerprint sensor scan area. However, larger sensors generally use more power, and power consumption is a key design constraint in mobile devices.

Accordingly, aspects of the present disclosure provide techniques for alleviating such power consumption concerns. For example, aspects of the present disclosure provide techniques for selectively activating the fingerprint sensor in response to detecting a finger hover above the display module of the electronic device. Accordingly, the fingerprint sensor may primarily remain in a low power mode until a finger hover above the display module of the electronic device is detected, saving power. In some cases, the finger hover may be detected using a planar pressure wave. In other cases, the finger hover may be detected using beamformed pressure waves. Due to acoustic interference concerns, aspects of the present disclosure also provide techniques for improving beamforming of pressure waves to detect the finger hover, as explained below.

FIG. 2is a flow diagram illustrating example operations200for activating a fingerprint sensor in a device comprising a display module, in accordance with certain aspects presented herein. According to aspects, operations200may be performed, for example, by one or more processors, such as the controller module106and/or processor904.

Operations200begin at block205with detecting a finger hover of a user of the device above the display module.

At block210, the one or more processors activate the fingerprint sensor based, at least in part, on the detected finger hover.

In some cases, activating the fingerprint sensor may mean activating a more-advanced processing capability associated with the fingerprint sensor. For example, in some cases, as explained below, the finger print sensor may itself be used to detect the finger hover. In such cases, the fingerprint sensor may be operating in a power saving mode, expending just enough power to emit pressure waves and detect a reflection of a finger hovering above the display module, for example, as opposed to operating in a more-advanced processing mode in which the fingerprint sensor is capable of scanning the actual fingerprints on the finger (which may consume a significant amount of power).

In other cases, a different means may be used to detect the finger hover, allowing the fingerprint sensor to remain in an off state until the finger hover is detected.

At block215, the one or more processors provide, in response to detecting the finger hover, feedback information to assist in scanning the finger using the fingerprint sensor. In some cases, the feedback may also be provided in response to activating the fingerprint sensor. According to aspects, the feedback may be any type of feedback that assists the user in scanning the finger, such as visual, audio, haptic, and the like.

FIG. 3provides an illustration of the techniques for detecting a finger hover and selectively activating a fingerprint sensor of an electronic device100, in accordance with certain aspects presented herein.

For example, as illustrated, at some point in time, a user of the electronic device100may position a finger over (e.g., hovering over and not touching) the display module102, which may be detected by the electronic device100. In some cases, the electronic device100may detect the finger hover based on at least one of an inductance-based sensor, a capacitance-based sensor, an optical-based sensor, or an sound-based sensor (e.g., the fingerprint sensor104).

In response to detecting the finger hover, the fingerprint sensor104in the electronic device100may be activated.

As noted above, the fingerprint sensor104an ultrasonic fingerprint sensor configured for sensing fingerprints based on pressure waves (e.g., ultrasonic pressure waves). In other words, the fingerprint sensor104may remain in a power-saving mode, reducing the power consumed by the fingerprint sensor104, until a finger hover is detected.

Further, in response to detecting the finger hover, a feedback module302in the electronic device100may generate and provide feedback information to assist in scanning the finger using the fingerprint sensor104. The feedback may be any type of feedback that assists in scanning the finger, such as visual feedback displayed on a screen304of the display module102, haptic feedback, auditory feedback, and the like.

For example, in some cases, the feedback module302may generate and display visual feedback, instructing a user where to scan the finger on the screen304. In other words, in response to the detected finger hover, the display module102may be activated and feedback displayed on the screen304of the display module102. In some cases, haptic feedback (e.g., vibration) may be provided throughout the electronic device. In other cases, the haptic feedback may be localized in an area of the electronic device100underneath the finger hover301. Additionally, in some cases, haptic feedback may be provided by a force sensor or a tactile sensor.

In some cases, another way to reduce power consumed by the fingerprint sensor104may be to activate only a portion of a larger area of the fingerprint sensor104.

In some cases, the portion of the larger area may comprise a fixed portion. For example, in some cases, only a fixed portion of the fingerprint sensor104underneath the portion306of the screen304may be activated, leaving a remaining portion of the fingerprint sensor inactivated and saving power. As shown, the fixed portion may correspond to a bottom portion of the fingerprint sensor104. According to aspects, the feedback information provided by the feedback module302may inform the user of the electronic device100to scan the finger on the portion306of the screen304.

In some cases, the portion of the larger area of the fingerprint sensor104may be a variable portion. For example, in some cases, the variable portion may correspond to an area of the fingerprint sensor underneath the finger hover, such as the variable portion308. For example, in some cases, when the finger hover301is detected, a general position associated with the finger hover301may also be determined. Accordingly, the variable portion308may correspond to the determined position of the finger hover301.

In other cases, the electronic device100may determine the variable portion308based on at least one of a pattern of usage of the device by the user and a finger touch area range associated with the finger. For example, in some cases, the electronic device100may collect statistics regarding where a user of the electronic device100most often touches the screen304. Accordingly, the variable portion308may then be set to the area of the screen304that the user most often touches. According to aspects, the feedback information provided by the feedback module302may inform the user of the electronic device100to scan the finger on the variable portion308of the screen304that the user most often touches. In some cases, if the user tries to scan the finer in an incorrect area, the feedback module302may provide additional feedback to the user to help correct the improper scan, such as directing the user to scan the finger in the variable portion308.

Additionally, as noted, in some cases, the electronic device100may take into account a finger touch area range associated with the finger. For example, in some cases, the electronic device may be able to deduce a type of the finger (e.g., thumb, index, etc.) and use this information to appropriately set the variable portion308. Further, in some cases, the variable portion308may be adjustable based on a size of the finger. For example, in some cases, the variable portion308corresponding to a thumb may be larger than the variable portion308corresponding to an index finger.

Further, in addition to depending on the finger hover301, the variable portion308may, in some cases, also be based on an area in which the finger touches the screen304. For example, in some cases, the variable portion308may be set to a first location of the screen304. Upon detecting the finger touching the screen304, the electronic device100may determine how much of the finger is inside the first location of the variable portion308and how much of the finger is outside the first location of the variable portion308. Based on these determinations, the electronic device100may deduce a second location of the screen304for the variable portion308such that the finger touch is located fully within the second location of the screen304for the variable portion308.

According to aspects, in response to detecting the finger hover301only the variable portion308of the fingerprint sensor104may be activated or transitioned from a power saving mode into a different mode. By only activating the variable portion308of the fingerprint sensor104, power consumption by the fingerprint sensor104may be reduced as compared to activating the fingerprint sensor104as a whole. Further, according to aspects, regardless of the position of the variable portion308, the feedback information provided by the feedback module302may inform the user of the electronic device100to scan the finger on a portion of the screen304corresponding to the variable portion308.

As noted above, in some cases, the finger hover301may be detected using the fingerprint sensor104. More specifically, for example, in some cases, detecting the finger hover comprises emitting pressure waves from the fingerprint sensor104(e.g., via a pressure wave module401illustrated inFIG. 4) through different portions of the display module102and detecting the finger hover above at least one portion of the different portions of the display module102, as described above.

It should be understood that, while aspects of the present disclosure describe techniques for selectively activating a fingerprint sensor based on a detected finger over, these techniques may apply equally to other types of detected bodily hovers. For example, in some cases, the techniques presented herein for detecting the finger hover and activating the fingerprint sensor based on the finger hove may apply equally to a detected hand hovering above or waved across (e.g., either close-fisted or open-fisted) the display module, as well as other appendages, such as arms, feet, etc.

In some cases, detecting the finger hover may be based on a planar pressure wave emitted by the fingerprint sensor104via a pressure wave module. For example, the pressure waves may be emitted in a kilohertz range and may be emitted such that at least one planar wave emitted through the different portions of the display module102of the electronic device100. For example, as illustrated inFIG. 4, a pressure wave module401in the fingerprint sensor104may include a plurality of transducers402configured to emit pressure waves404. According to aspects, the controller module106may be configured to control different sets of transducers of the plurality of transducers402to selectively emit the pressure waves404, generating a planar pressure wave406. The planar pressure wave406may then be directed across the screen304by selectively controlling the different sets of transducers.

According to aspects, once the planar pressure wave406is directed into an area beneath the finger hover301, a plurality of pressure waves may be reflected by the finger and received by the pressure wave module401, allowing the fingerprint sensor104to detect the finger hover301. For example, in some cases, detecting the finger may be based on a certain receive signal strength of pressure waves reflected from the finger. For example, in some cases, the pressure wave module401may receive a plurality of response pressure waves in response to the planar pressure wave406. According to aspects, if the plurality of response pressure waves received by the pressure wave module401have a signal strength above a certain threshold, the fingerprint sensor104may detect the finger hover301.

In some cases, such techniques of using a planar pressure wave406to detect the finger hover301may be better suited when used with pressure waves at certain frequencies, such as pressure waves emitted in the kilohertz range, due to the way in which certain pressure waves propagate through air. For example, pressure waves in the kilohertz range may be better at propagating through the air, allowing for the finger hover301to be detected at a greater distance (e.g., several millimeters) above the display module102as opposed to pressure waves in, for example, a megahertz range (e.g., ultrasound). For example, pressure waves in the megahertz range may quickly attenuate at an interface between the screen304and air surrounding the electronic device100, preventing the finger hover301from being detected more than a few micrometers above the display module102.

However, a problem that may be experienced by using pressure waves in the kilohertz range is that such pressure waves can be heard whereas ultrasonic pressure waves are generally inaudible to humans. Being able to hear the pressure waves while trying to scan a fingerprint may be irritating to some users. Therefore, techniques presented herein provide techniques to improving the use of ultrasonic pressure wave (e.g., which are generally inaudible to most users) such that a finger hover may be detected at greater distances above the display module102. Such techniques may involve beamforming ultrasonic pressure wave through different portions of the display module102, providing for a better received signal strength associated with pressure waves reflected off of a hovering finger and allowing the finger to be detected at greater distances above the display module102. Aspects of the present disclosure also provide techniques for improving beamforming, which take into account different design considerations associated with the fingerprint sensor104and display module102.

Techniques for Beamforming Pressure Waves

FIG. 5is a flow diagram illustrating example operations500for activating the fingerprint sensor of the electronic device based on beamformed pressure waves, in accordance with certain aspects presented herein. According to aspects, operations200may be performed, for example, by one or more processors, such as the controller module106and/or processor904.

Operations500begin at block505with emitting, via a pressure wave module of the apparatus, beamformed ultrasonic pressure waves through a display module of the apparatus.

At block510, the one or more processors receive, via the pressure wave module, at least one response pressure wave in response to the beamformed ultrasonic pressure waves.

At block515, the one or more processors detect a finger hover above the display module based on the at least one response pressure wave.

At block520, the one or more processors activates a fingerprint sensor based on the detected finger hover.

As noted, in some cases, detecting a finger hover may be based on beamforming pressure waves emitted by the fingerprint sensor104. For example,FIG. 6illustrates detecting the finger hover based on beamformed pressure waves, in accordance with certain aspects of the present disclosure.

As illustrated inFIG. 6, the pressure wave module401in the fingerprint sensor104may include a plurality of transducers402configured to emit pressure waves404. In some cases, the pressure waves404may be emitted in a megahertz (e.g., ultrasound) range. According to aspects, the controller module106may be configured to control different sets of transducers of the plurality of transducers402to selectively emit the pressure waves404, generating a beamformed pressure wave602. For example, as illustrated, the control module106may be configured to control transducers604of the pressure wave module401to emit pressure waves404. The controller module106may control the transducers604to emit the pressure waves404such that the pressure waves constructively and destructively interfere with each other to form the beamformed pressure wave602.

In some cases, controller module106may control the formation of the beamformed pressure wave602by controlling the time the pressure waves404are emitted from each of the transducers604. The controller module106may then steer the beamformed pressure wave602through different portions of the display module102by selectively controlling different sets of the transducers402. Additionally, in some cases, the controller module106may change a direction or a focal depth of the beamformed pressure wave602by operating only a subset of the transducers402in the fingerprint sensor104or operating the one or more the transducers402according to a time delay pattern.

Accordingly, focusing the pressure waves404in such a manner increases a transmit power associated with the beamformed pressure wave602. Increasing the transmission power associated with the pressure waves404(e.g., via the beamformed pressure wave602) may result in a greater receive power of response waves reflected by the finger and allows the finger hover201to be detected at greater distances (e.g., several millimeters above the display module102) as compared to using a planar ultrasonic wave whose transmit power is spread across a plane.

Accordingly, as noted, the controller module106may selectively control the transducers402of the pressure wave module401to steer the beamformed pressure wave602through different portions of the display module102.

In some cases, the pressure wave module may receive at least one response pressure wave (e.g., a reflected pressure wave) in response to the beamformed ultrasonic pressure waves. Based on the at least one response pressure wave, a finger hover201above the display module102may be detected.

For example, one or more pressure waves may be reflected off of the finger and received at the pressure wave module. Based on the one or more reflected response pressure waves, the finger hover may be detected.

In response to detecting the finger hover, the fingerprint sensor may be activated. In some cases, detecting the finger may be based on a certain receive signal strength of the reflected response pressure waves. For example, in some cases, the pressure wave module401receive a plurality of reflected response pressure waves in response to the beamformed pressure wave602. According to aspects, if the plurality of reflected response pressure waves received by the pressure wave module401have a signal strength above a certain threshold, the fingerprint sensor104may detect the finger hover301.

As noted above, certain aspects of the present disclosure explain that the fingerprint sensor may itself detect the finger hover. In such cases, activating the fingerprint sensor may include transitioning the fingerprint sensor from a power saving mode that uses a minimal amount of power and processing capability for beamforming a pressure wave to more-advanced processing mode that allows the fingerprint sensor to detect fingerprints on the finger. In other cases, when the finger hover is detected using a different type of sensor (e.g., an inductance-based sensor, a capacitance-based sensor, an optical-based sensor, etc.) the fingerprint sensor may be powered off or remain in a lower power mode. Upon detection of the finger hover by the different type of sensor, the fingerprint sensor may be transitioned to the more-advanced processing mode that allows the fingerprint sensor to detect fingerprints on the finger.

In certain cases, beamforming of ultrasonic pressure waves through the display module102may be improved by using different design constraints for the display module102and fingerprint sensor104. For example, as noted above, the display module102may comprise a first plurality of layers and the pressure wave module401of the fingerprint sensor104may comprise a second plurality of layers.

In some cases, as illustrated inFIG. 7A, the first plurality of layers of the display module102may comprise, for example, a cover glass layer702, a first optical clear adhesive (OCA) layer704disposed below the cover glass layer702, a polarizer layer706disposed below the first OCA layer704, a back plate pressure sensitive adhesive (BPSA) layer708disposed below the polarizer layer706, a touch sensor layer710disposed below the BPSA layer708, a second OCA layer712disposed below the touch sensor layer710, and a display panel714disposed below the second OCA layer712.

According to aspects, the second plurality of layers of the pressure wave module401may include, for example, a thin film transistor (TFT) glass layer716, a copolymer layer718, a conductive layer720, and a dielectric protection layer722. According to aspects, the copolymer layer718may include a plurality of elements each configured to generate ultrasonic pressure waves (e.g.,404), such as the transducers402. Further, in some cases, the TFT glass layer716may comprise circuitry configured to collectively control (e.g., via the controller module106) the plurality of elements (e.g., transducers402) in the copolymer layer718to generate an ultrasonic pressure wave beam (e.g.,602) using the ultrasonic pressure waves and steer the ultrasonic pressure wave beam through the display module102. Additionally, in some cases, the dielectric protection layer (e.g., a die attached film layer) may be configured to prevent corrosion associated with the pressure wave module401.

Further, in some cases, a size of each of the elements in the plurality of elements and a spacing between the elements in the plurality of elements may depend, at least in part, on a focal depth and a signal strength of the ultrasonic pressure wave beam (e.g.,602) required to detect a finger hover over the display module at a predefined distance. For example, in some cases, it may be desired to detect a finger hover five millimeters above the display module with a receive signal strength of X dB. In this case, a size of each of the elements (e.g., transducers402) and a spacing between each of the elements may be set such that the finger hover may be detected at least 5 millimeters above the display module and with a receive signal strength of at least X db.

In some cases, an order of the second plurality of layers in the pressure wave module401may depend on an acoustic resonance value associated with the display module102. For example, in some cases, the ordering of the second plurality of layers may be determined such that an acoustic resonance value of the ordered second plurality of layers closely matches the acoustic resonance value of the first plurality of layers. According to aspects, matching the acoustic resonance values of the second plurality of layers with the first plurality of layers may allow ultrasonic pressure waves to more-easily pass through the display module102without much attenuation at an interface between the display module102and the pressure wave module103.

FIGS. 7A-7Cillustrate different orderings for the pressure wave module401, in accordance with certain aspects presented herein. For example, as illustrated inFIG. 7A, the ordering of the pressure wave module401may comprise the TFT glass layer716being disposed below a bottom layer of the first plurality of layers of the display module102(e.g., such as the display panel714), the copolymer layer718being disposed below the TFT glass layer716, the conductive layer720being disposed below the copolymer layer718, and the dielectric protection layer722being disposed below the conductive layer720.

As illustrated inFIG. 7B, the ordering of the pressure wave module401may comprise the copolymer layer718being disposed below a bottom layer of the first plurality of layers of the display module (e.g., the display panel714), the conductive layer720being disposed below the copolymer layer718, the dielectric protection layer722being disposed below the conductive layer720, and the TFT glass layer716being disposed below the dielectric protection layer722.

As illustrated inFIG. 7C, the ordering of the pressure wave module401may comprise the dielectric protection layer722being disposed below a bottom layer of the first plurality of layers of the display module (e.g., the display panel714), the conductive layer720being disposed below the dielectric protection layer722, the copolymer layer718being disposed below the conductive layer720, and the TFT glass layer716being disposed below the copolymer layer718.

According to aspects, the pressure wave module401may be configured to generate ultrasonic pressure waves at a frequency. Further, the pressure wave module401may be coupled with the display module102by an adhesive layer724. In some cases, a thickness of the adhesive layer724may be configured to be one of a half-wavelength or one quarter-wavelength of the frequency at which the pressure wave module401is configured to generate and emit the ultrasonic pressure waves. Such thickness may help match the acoustic resonance values of the pressure wave module401and display module102, allowing for a stronger output signal. For example, the adhesive layer724may be considered a matching layer that matches the acoustic impedances between two neighboring layers. Depending on the acoustic impedances of the neighboring layers, the thickness of the adhesive layer724can be either a half wavelength or a quarter wavelength. For example, in some cases, when each neighboring layer has a larger impedance as compared to the adhesive layer724, the thickness of the adhesive layer724may be a half wavelength, whereas if one neighboring layer has a larger acoustic impedance while the other neighboring layer has a smaller acoustic impedance, the thickness of the adhesive layer724may be a quarter wavelength.

Additionally, in some cases, a spacer layer726may be disposed between the display module102and the pressure wave module401and, In some cases, the spacer layer726may be composed of a plastic material, such as polyethylene terephthalate, and may help mitigate effects caused to a response signal associated with spatial resolution (e.g., line-pairs per millimeter (LPMM)) received by the pressure wave module401. In other words, the spacer layer726may affect a spatial resolution associated with a response signal received by the pressure wave module401. In some cases, the spacer layer726may be disposed between the display module102and the adhesive layer724. In other cases, for example as illustrated inFIGS. 7A-7C, the spacer layer726may be disposed between the adhesive layer724and pressure wave module401.

According to aspects, in order to get the best output signal (e.g., beamformed pressure wave502), the second plurality of layers of the pressure wave module401may be optimized, taking into account the resonance of the pressure wave module401itself. For example, the resonance of the pressure wave module401may be determined by the thickness of each individual layer of the second plurality of layers. Accordingly, to obtain the best output signal, the effective thickness of the pressure wave module401may be configured to be an odd multiple of a quarter of a wavelength associated with the ultrasonic pressure waves, wherein the wavelength of the ultrasonic pressure waves is based on a speed of sound in each of the second plurality of layers and the frequency of the ultrasonic pressure waves.

FIG. 8illustrates an electronic device800that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in, and described in relation to,FIGS. 2-4 and 6. In some cases, the electronic device800may comprise the electronic device100illustrated inFIGS. 1, 3, 4, and 6The electronic device800includes a processing system802configured to perform processing functions for the electronic device800. For example, in some cases, the processing system802may be configured to control a fingerprint sensor810to generate and emit, via a pressure wave module812in the fingerprint sensor810, pressure waves through a display module814of the electronic device800. In response to the emitted pressure waves, the processing system802may detect a finger hover above the display module814and provide feedback information via a feedback module816.

The processing system802includes a processor804coupled to a computer-readable medium/memory806via a bus808. In certain aspects, the computer-readable medium/memory806is configured to store instructions (e.g., computer-executable code) that when executed by the processor804, cause the processor804to perform the operations illustrated inFIG. 2, or other operations for performing the various techniques discussed herein for activating the fingerprint sensor810of the electronic device800. In certain aspects, computer-readable medium/memory806stores code818for detecting a finger hover above the display module814; code820for activating the fingerprint sensor810based, at least in part, on the detected finger hover; and code822for providing, in response to detecting the finger hover, feedback information via the feedback module816to assist in scanning the finger using the fingerprint sensor810.

In certain aspects, the processor804includes circuitry configured to implement the code stored in the computer-readable medium/memory806. For example, the processor804includes circuitry824for detecting a finger hover above the display module814; circuitry826for activating the fingerprint sensor810based, at least in part, on the detected finger hover; and circuitry828for providing, in response to detecting the finger hover, feedback information via the feedback module816to assist in scanning the finger using the fingerprint sensor810.

FIG. 9illustrates an electronic device900that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in, and described in relation to,FIGS. 5 and 6. In some cases, the electronic device900may comprise the electronic device100illustrated inFIG. 6The electronic device900includes a processing system902configured to perform processing functions for the electronic device900. For example, in some cases, the processing system902may be configured to control a fingerprint sensor910to generate and emit, via a pressure wave module912in the fingerprint sensor910, beamformed ultrasonic pressure waves through a display module914of the electronic device900. In response to the emitted beamformed ultrasonic pressure waves, the pressure wave module912may receive at least one response pressure wave. Accordingly, based on the at least one response pressure wave, the processing system902may detect a finger hover above the display module914.

The processing system902includes a processor904coupled to a computer-readable medium/memory906via a bus908. In certain aspects, the computer-readable medium/memory906is configured to store instructions (e.g., computer-executable code) that when executed by the processor904, cause the processor904to perform the operations illustrated inFIG. 5, or other operations for performing the various techniques discussed herein for activating the fingerprint sensor910of the electronic device900based on beamformed pressure waves. In certain aspects, computer-readable medium/memory906stores code918for emitting, via the pressure wave module912of, beamformed ultrasonic pressure waves through the display module914; code920for receiving, via the pressure wave module912, at least one response pressure wave in response to the beamformed ultrasonic pressure waves; code922for detecting a finger hover above the display module914based on the at least one response pressure wave; and code924for activating the fingerprint sensor910based on the detected finger hover.

In certain aspects, the processor904includes circuitry configured to implement the code stored in the computer-readable medium/memory906. For example, the processor904includes circuitry926for emitting, via the pressure wave module912of, beamformed ultrasonic pressure waves through the display module914; circuitry928for receiving, via the pressure wave module912, at least one response pressure wave in response to the beamformed ultrasonic pressure waves; circuitry930for detecting a finger hover above the display module914based on the at least one response pressure wave; and circuitry932for activating the fingerprint sensor910based on the detected finger hover.

Additional Considerations