Patent Application
20200409191
This disclosure relates to optical fingerprint sensors, and, more particularly, to enhancement films for under-screen optical fingerprint sensors, such as optical fingerprint sensors integrated within a display panel arrangement of mobile devices, wearable devices, and other computing devices.
Various sensors can be implemented in electronic devices or systems to provide certain desired functions. A sensor that enables user authentication is one example of sensors to protect personal data and prevent unauthorized access in various devices and systems including portable or mobile computing devices (e.g., laptops, tablets, smartphones), gaming systems, various databases, information systems or larger computer-controlled systems.
User authentication on an electronic device or system can be carried out through one or multiple forms of biometric identifiers, which can be used alone or in addition to conventional password authentication methods. A popular form of biometric identifiers is a person's fingerprint pattern. A fingerprint sensor can be built into the electronic device to read a user's fingerprint pattern so that the device can only be unlocked by an authorized user of the device through authentication of the authorized user's fingerprint pattern. Another example of sensors for electronic devices or systems is a biomedical sensor that detects a biological property of a user, e.g., a property of a user's blood, the heartbeat, in wearable devices like wrist band devices or watches. In general, different sensors can be provided in electronic devices to achieve different sensing operations and functions.
Fingerprints can be used to authenticate users for accessing electronic devices, computer-controlled systems, electronic databases or information systems, either used as a stand-alone authentication method or in combination with one or more other authentication methods such as a password authentication method. For example, electronic devices including portable or mobile computing devices, such as laptops, tablets, smartphones, and gaming systems can employ user authentication mechanisms to protect personal data and prevent unauthorized access. In another example, a computer or a computer-controlled device or system for an organization or enterprise should be secured to allow only authorized personnel to access in order to protect the information or the use of the device or system for the organization or enterprise. The information stored in portable devices and computer-controlled databases, devices or systems, may be personal in nature, such as personal contacts or phonebook, personal photos, personal health information or other personal information, or confidential information for proprietary use by an organization or enterprise, such as business financial information, employee data, trade secrets and other proprietary information. If the security of the access to the electronic device or system is compromised, these data may be accessed by others, causing loss of privacy of individuals or loss of valuable confidential information. Beyond security of information, securing access to computers and computer-controlled devices or systems also allow safeguard the use of devices or systems that are controlled by computers or computer processors such as computer-controlled automobiles and other systems such as ATMs.
Secured access to a device (e.g., a mobile device) or a system (e.g., an electronic database and a computer-controlled system) can be achieved in different ways such as the use of user passwords. A password, however, may be easily to be spread or obtained and this nature of passwords can reduce the level of the security of passwords. Moreover, since a user needs to remember a password in accessing password-protected electronic devices or systems, in the event that the user forgets the password, the user needs to undertake certain password recovery procedures to get authenticated or otherwise to regain the access to the device or system. Such processes may be burdensome to users and have various practical limitations and inconveniences. The personal fingerprint identification can be utilized to achieve the user authentication for enhancing the data security while mitigating certain undesired effects associated with passwords.
Electronic devices or systems, including portable or mobile computing devices, may employ user authentication through one or multiple forms of biometric identifiers to protect personal or other confidential data and prevent unauthorized access. A biometric identifier can be used alone or in combination with a password authentication method to provide user authentication. One form of biometric identifiers is a person's fingerprint pattern. A fingerprint sensor can be built into an electronic device or an information system to read a user's fingerprint pattern so that the device can only be unlocked by an authorized user of the device through authentication of the authorized user's fingerprint pattern.
Embodiments provide improved optical enhancement panels for liquid crystal modules integrated in electronic devices. For example the enhancement panel can be a backlight enhancement panel for use in electronic devices having an integrated optical fingerprint sensor. The enhancement panels include a set of enhancement film layers, each with prism structures having trapezoidal ridges and/or trapezoidal valleys. The trapezoidal prism features can provide prismatic enhancement properties for light passing through the enhancement panel in one direction, while providing clear viewing windows for light passing through the enhancement panel in the opposite direction. For example, the novel enhancement layers can provide backlight enhancement, while reducing blurring of reflected probe light used for optical sensing.
According to one set of embodiments, an electronic device is provided having an integrated under-screen optical sensor. The electronic device includes: a liquid crystal module (LCM) comprising a plurality LCM layers, the plurality of LCM layers including: a liquid crystal display panel having a plurality of liquid crystal structures to output images for display, and a plurality of touch-sensing structures to detect touch events; and an enhancement panel having a set of enhancement film layers, each enhancement film layer comprising a plurality of prism structures, each prism structure defined by a set of prism features including a prism ridge and a prism valley, at least one of the set of prism features of each prism structure having a trapezoidal profile, each prism ridge pointing toward the liquid crystal display panel; an optical sensor module disposed below the LCM to receive probe light that passes through the liquid crystal display panel to detect an optical biometric feature, the optical sensor module comprising an optical sensor array to receive the probe light; and a top transparent layer disposed above the LCM to provide an output interface for displaying the images, an input interface for receiving the touch events, and an input interface to provide an optical path between the optical biometric feature and the liquid crystal display panel.
In some such embodiments, at least a portion of the prism structures are trapezoidal-ridge prism structures, such that the set of prism features of at least the portion of the prism structures comprises a plurality of flattened ridge features and a plurality of sharp valley features. For example, the enhancement panel includes: an upper enhancement film layer comprising a first portion of the plurality of prism structures running in a first direction to form a first plurality of flat ridge lines; and a lower enhancement film layer comprising a second portion of the plurality of prism structures running in a second direction to form a second plurality of flat ridge lines, the second direction being orthogonal to the first direction; and a ridge-ridge clear viewing window is formed at each location where one of the first plurality of flat ridge lines crosses one of the second plurality of flat ridge lines.
In other such embodiments, at least a portion of the prism structures are trapezoidal-valley prism structures, such that the set of prism features of at least the portion of the prism structures comprises a plurality of flattened valley features and a plurality of sharp ridge features. For example, the enhancement panel includes: an upper enhancement film layer comprising a first portion of the plurality of prism structures running in a first direction to form a first plurality of flat valley lines; and a lower enhancement film layer comprising a second portion of the plurality of prism structures running in a second direction to form a second plurality of flat valley lines, the second direction being orthogonal to the first direction; and a valley-valley clear viewing window is formed at each location where one of the first plurality of flat valley lines crosses one of the second plurality of flat valley lines.
In other embodiments, at least a portion of the prism structures are trapezoidal-ridge-trapezoidal-valley prism structures, such that the set of prism features of at least the portion of the prism structures comprises a plurality of flattened ridge features and a plurality of flattened valley features. For example, the enhancement panel includes: an upper enhancement film layer comprising a first portion of the plurality of prism structures running in a first direction to form a first plurality of flat ridge lines and a first plurality of flat valley lines; and a lower enhancement film layer comprising a second portion of the plurality of prism structures running in a second direction to form a second plurality of flat ridge lines and a second plurality of flat valley lines, the second direction being orthogonal to the first direction; a ridge-ridge clear viewing window is formed at each location where one of the first plurality of flat ridge lines crosses one of the second plurality of flat ridge lines; a valley-valley clear viewing window is formed at each location where one of the first plurality of flat valley lines crosses one of the second plurality of flat valley lines; and a ridge-valley clear viewing window is formed at each location where one of the first plurality of flat ridge lines crosses one of the second plurality of flat valley lines, and at each location where one of the first plurality of flat valley lines crosses one of the second plurality of flat ridge lines.
In some embodiments, the liquid crystal display panel has a top display surface facing the top transparent layer and a bottom display surface facing the enhancement panel; the bottom display surface has, applied thereon, an index-matching layer; and for one of the set of enhancement film layers, each of at least a portion of the prism structures is formed to have a corresponding sharp prism ridge having a peak portion disposed within the index-matching layer to form a corresponding trapezoidal-ridge prism structure. Additionally or alternatively, the enhancement panel can include an upper enhancement film layer and a lower enhancement film layer; the upper enhancement film layer has a top film surface facing the liquid crystal display panel and a lower film surface facing the lower enhancement film layer; the bottom film surface has, applied thereon, an index-matching layer; and for the lower enhancement film layer, each of at least a portion of the prism structures is formed to have a corresponding sharp prism ridge having a peak portion disposed within the index-matching layer to form a corresponding trapezoidal-ridge prism structure.
In some embodiments, each of the set of enhancement film layers is an optically polarized enhancement film layer. In some embodiments, one or more probe light sources under the liquid crystal display panel to project the probe light toward a sensor region of the top transparent layer through the enhancement panel and the liquid crystal display panel, such that a reflected portion of the probe light is received from the sensor region of the top transparent layer by the optical sensor module. In some embodiments, the top transparent layer includes a designated sensing region located relative to the optical sensor module, such that interfacing of the optical biometric feature with the designated sensing region permits sensing of the optical biometric feature by the optical sensor module. In some embodiments, the liquid crystal display panel structure includes a light diffuser layer configured to permit transmission of light to the optical sensor module. In some embodiments, the plurality of LCM layers further includes at least one of: a light guide plate layer; or a light reflector layer.
According to another set of embodiments, a liquid crystal module (LCM) is provided for integration in an electronic device having an integrated under-screen optical sensor. The LCM includes: a liquid crystal display panel having a plurality of liquid crystal structures to output images for display; an enhancement panel disposed below the liquid crystal display panel and having a set of enhancement film layers, each enhancement film layer comprising a plurality of prism structures, each prism structure defined by a set of prism features including a prism ridge and a prism valley, at least one of the set of prism features of each prism structure having a trapezoidal profile, each prism ridge pointing toward the liquid crystal display panel; one or more backlight sources disposed below the enhancement panel and arranged to provide backlighting to the liquid crystal display panel through the enhancement panel; one or more probe light sources disposed below the enhancement panel and arranged to project probe light through the enhancement panel and the liquid crystal display panel corresponding to a sensor region, such that when the LCM is sandwiched between a top transparent layer and an optical sensor module, the probe light is projected onto sensor portion of the top transparent layer, and a reflected portion of the probe light is received from the sensor region of the top transparent layer by the optical sensor module.
The accompanying drawings, referred to herein and constituting a part hereof, illustrate embodiments of the disclosure. The drawings together with the description serve to explain the principles of the invention.
In the appended figures, similar components and/or features can have the same reference label. Further, various components of the same type can be distinguished by following the reference label by a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.
In the following description, numerous specific details are provided for a thorough understanding of the present invention. However, it should be appreciated by those of skill in the art that the present invention may be realized without one or more of these details. In other examples, features and techniques known in the art will not be described for purposes of brevity.
Electronic devices or systems may be equipped with fingerprint authentication mechanisms to improve the security for accessing the devices. Such electronic devices or system may include, portable or mobile computing devices, e.g., smartphones, tablet computers, wrist-worn devices and other wearable or portable devices, larger electronic devices or systems, e.g., personal computers in portable forms or desktop forms, ATMs, various terminals to various electronic systems, databases, or information systems for commercial or governmental uses, motorized transportation systems including automobiles, boats, trains, aircraft and others.
Fingerprint sensing is useful in mobile applications and other applications that use or require secure access. For example, fingerprint sensing can be used to provide secure access to a mobile device and secure financial transactions including online purchases. It is desirable to include robust and reliable fingerprint sensing suitable for mobile devices and other applications. In mobile, portable or wearable devices, it is desirable for fingerprint sensors to minimize or eliminate the footprint for fingerprint sensing given the limited space on those devices, especially considering the demands for a maximum display area on a given device. Many implementations of capacitive fingerprint sensors must be implemented on the top surface of a device due to the near-field interaction requirement of capacitive sensing.
Optical sensing modules can be designed to mitigate the above and other limitations in the capacitive fingerprint sensors and to achieve additional technical advantages. For example, in implementing an optical fingerprint sensing device, the light carrying fingerprint imagining information can be directed over distance to an optical detector array of optical detectors for detecting the fingerprint without being limited to the near-field sensing in a capacitive sensor. In particular, light carrying fingerprint imagining information can be directed to transmit through the top cover glass commonly used in many display screens such as touch sensing screens and other structures and may be directed through folded or complex optical paths to reach the optical detector array, thus allowing for flexibility in placing an optical fingerprint sensor in a device that is not available for a capacitive fingerprint sensor. Optical fingerprint sensor modules based on the technologies disclosure herein can be an under-screen optical fingerprint sensor module that is placed below a display screen to capture and detect light from a finger placed on or above the top sensing surface of the screen. As disclosed herein, optical sensing can also be used to, in addition to detecting and sensing a fingerprint pattern, optically detect other parameters associated with a user or a user action, such as whether a detected fingerprint is from a finger of a live person and to provide anti-spoofing mechanism, or certain biological parameters of the user.
The optical sensing technology and examples of implementations described in this disclosure provide an optical fingerprint sensor module that uses, at least in part, the light from a display screen as the illumination probe light to illuminate a fingerprint sensing area on the touch sensing surface of the display screen to perform one or more sensing operations based on optical sensing of such light. A suitable display screen for implementing the disclosed optical sensor technology can be based on various display technologies or configurations, including, a liquid crystal display (LCD) screen using a backlight to provide white light illumination to the LCD pixels and matched optical filters to effectuate colored LCD pixels, or a display screen having light emitting display pixels without using backlight where each individual pixel generates light for forming a display image on the screen such as an organic light emitting diode (OLED) display screens, or electroluminescent display screens. The specific examples provided below are directed to integration of under-screen optical sensing modules with LCD screens and thus contain certain technical details associated with LCD screens although various aspects of the disclosed technology are applicable to OLED screens and other display screens.
A portion of the light produced by a display screen for displaying images necessarily passes through the top surface of the display screen in order to be viewed by a user. A finger in touch with or near the top surface interacts with the light at the top surface to cause the reflected or scattered light at the surface area of the touch to carry spatial image information of the finger. Such reflected or scattered light carrying the spatial image information of the finger returns to the display panel underneath the top surface. In touch sensing display devices, for example, the top surface is the touch sensing interface with the user and this interaction between the light for displaying images and the user finger or hand constantly occurs but such information-carrying light returning back to the display panel is largely wasted and is not used in various touch sensing devices. In various mobile or portable devices with touch sensing displays and fingerprint sensing functions, a fingerprint sensor tends to be a separate device from the display screen, either placed on the same surface of the display screen at a location outside the display screen area such as in some models of Apple iPhones and Samsung smartphones, or placed on the backside of a smartphone, such as some models of smart phones by Huawei, Lenovo, Xiaomi or Google, to avoid taking up valuable space for placing a large display screen on the front side. Those fingerprint sensors are separate devices from the display screens and thus need to be compact to save space for the display screens and other functions while still providing reliable and fast fingerprint sensing with a spatial image resolution above a certain acceptable level. However, the need to be compact and small for designing a fingerprint sensor and the need to provide a high spatial image resolution in capturing a fingerprint pattern are in direct conflict with each other in many fingerprint sensors because a high spatial image resolution in capturing a fingerprint pattern in based on various suitable fingerprint sensing technologies (e.g., capacitive touch sensing or optical imaging) requires a large sensor area with a large number of sensing pixels.
The sensor technology and examples of implementations of the sensor technology described in this disclosure provide an optical fingerprint sensor module that uses, at least in part, the light from a display screen as the illumination probe light to illuminate a fingerprint sensing area on the touch sensing surface of the display screen to perform one or more sensing operations based on optical sensing of such light in some implementations, or designated illumination or probe light for optical sensing from one or more designated illumination light sources separate from the display light for optical sensing in other implementations, or background light for optical sensing in certain implementations.
In the disclosed examples for integrating an optical sensing module to a LCD screen based on the disclosed optical sensor technology, the under LCD optical sensor can be used to detect a portion of the light that is used for displaying images in a LCD screen where such a portion of the light for the display screen may be the scattered light, reflected light or some stray light. For example, in some implementations, the image light of the LCD screen based on backlighting may be reflected or scattered back into the LCD display screen as returned light when encountering an object such as a user finger or palm, or a user pointer device like a stylus. Such returned light can be captured for performing one or more optical sensing operations using the disclosed optical sensor technology. Due to the use of the light from LCD screen for optical sensing, an optical fingerprint sensor module based on the disclosed optical sensor technology is specially designed to be integrated to the LCD display screen in a way that maintains the display operations and functions of the LCD display screen without interference while providing optical sensing operations and functions to enhance overall functionality, device integration and user experience of an electronic device or system such as a smart phone, a tablet, or a mobile and/or wearable device.
In addition, in various implementations of the disclosed optical sensing technology, one or more designated probe light sources may be provided to produce additional illumination probe light for the optical sensing operations by the under-LCD screen optical sensing module. In such applications, the light from the backlighting of the LCD screen and the probe light from the one or more designated probe light sources collectively form the illumination light for optical sensing operations.
Regarding the additional optical sensing functions beyond fingerprint detection, the optical sensing may be used to measure other parameters. For example, the disclosed optical sensor technology can measure a pattern of a palm of a person given the large touch area available over the entire LCD display screen (in contrast, some designated fingerprint sensors such as the fingerprint sensor in the home button of Apple's iPhone/iPad devices have a rather small and designated off-screen fingerprint sensing area that is highly limited in the sensing area size that may not be suitable for sensing large patterns). For yet another example, the disclosed optical sensor technology can be used not only to use optical sensing to capture and detect a pattern of a finger or palm that is associated with a person, but also to use optical sensing or other sensing mechanisms to detect whether the captured or detected pattern of a fingerprint or palm is from a live person's hand by a “live finger” detection mechanism, which may be based on, for example, the different optical absorption behaviors of the blood at different optical wavelengths, the fact that a live person's finger tends to be moving or stretching due to the person's natural movement or motion (either intended or unintended) or pulsing when the blood flows through the person's body in connection with the heartbeat. In one implementation, the optical fingerprint sensor module can detect a change in the returned light from a finger or palm due to the heartbeat/blood flow change and thus to detect whether there is a live heartbeat in the object presented as a finger or palm. The user authentication can be based on the combination of the both the optical sensing of the fingerprint/palm pattern and the positive determination of the presence of a live person to enhance the access control. For yet another example, the optical fingerprint sensor module may include a sensing function for measuring a glucose level or a degree of oxygen saturation based on optical sensing in the returned light from a finger or palm. As yet another example, as a person touches the LCD display screen, a change in the touching force can be reflected in one or more ways, including fingerprint pattern deforming, a change in the contacting area between the finger and the screen surface, fingerprint ridge widening, or a change in the blood flow dynamics. Those and other changes can be measured by optical sensing based on the disclosed optical sensor technology and can be used to calculate the touch force. This touch force sensing can be used to add more functions to the optical fingerprint sensor module beyond the fingerprint sensing.
With respect to useful operations or control features in connection with the touch sensing aspect of the LCD display screen, the disclosed optical sensor technology can provide triggering functions or additional functions based on one or more sensing results from the optical fingerprint sensor module to perform certain operations in connection with the touch sensing control over the LCD display screen. For example, the optical property of a finger skin (e.g., the index of refraction) tends to be different from other artificial objects. Based on this, the optical fingerprint sensor module may be designed to selectively receive and detect returned light that is caused by a finger in touch with the surface of the LCD display screen while returned light caused by other objects would not be detected by the optical fingerprint sensor module. This object-selective optical detection can be used to provide useful user controls by touch sensing, such as waking up the smartphone or device only by a touch via a person's finger or palm while touches by other objects would not cause the device to wake up for energy efficient operations and to prolong the battery use. This operation can be implemented by a control based on the output of the optical fingerprint sensor module to control the waking up circuitry operation of the LCD display screen which, the LCD pixels are put in a “sleep” mode by being turned off (and the LCD backlighting is also turned off) while one or more illumination light sources (e.g., LEDs) for the under-LCD panel optical fingerprint sensor module are turned on in a flash mode to intermittently emit flash light to the screen surface for sensing any touch by a person's finger or palm. Under this design, the optical fingerprint sensor module operates the one or more illumination light sources to produce the “sleep” mode wake-up sensing light flashes so that the optical fingerprint sensor module can detect returned light of such wake-up sensing light caused by the finger touch on the LCD display screen and, upon a positive detection, the LCD backlighting and the LCD display screen are turned on or “woken up”. In some implementations, the wake-up sensing light can be in the infrared invisible spectral range so a user will not experience any visual of a flash light. The LCD display screen operation can be controlled to provide an improved fingerprint sensing by eliminating background light for optical sensing of the fingerprint. In one implementation, for example, each display scan frame generates a frame of fingerprint signals. If, two frames of fingerprint signals with the display are generated in one frame when the LCD display screen is turned on and in the other frame when the LCD display screen is turned off, the subtraction between those two frames of signals can be used to reduce the ambient background light influence. By operating the fingerprint sensing frame rate is at one half of the display frame rate in some implementations, the background light noise in fingerprint sensing can be reduced.
An optical fingerprint sensor module based on the disclosed optical sensor technology can be coupled to the backside of the LCD display screen without requiring creation of a designated area on the surface side of the LCD display screen that would occupy a valuable device surface real estate in some electronic devices such as a smartphone, a tablet or a wearable device. This aspect of the disclosed technology can be used to provide certain advantages or benefits in both device designs and product integration or manufacturing.
In some implementations, an optical fingerprint sensor module based on the disclosed optical sensor technology can be configured as a non-invasive module that can be easily integrated to a display screen without requiring changing the design of the LCD display screen for providing a desired optical sensing function such as fingerprint sensing. In this regard, an optical fingerprint sensor module based on the disclosed optical sensor technology can be independent from the design of a particular LCD display screen design due to the nature of the optical fingerprint sensor module: the optical sensing of such an optical fingerprint sensor module is by detecting the light that is emitted by the one or more illumination light sources of the optical fingerprint sensor module and is returned from the top surface of the display area, and the disclosed optical fingerprint sensor module is coupled to the backside of the LCD display screen as a under-screen optical fingerprint sensor module for receiving the returned light from the top surface of the display area and thus does not require a special sensing port or sensing area that is separate from the display screen area. Accordingly, such an under-screen optical fingerprint sensor module can be used to combine with a LCD display screen to provide optical fingerprint sensing and other sensor functions on an LCD display screen without using a specially designed LCD display screen with hardware especially designed for providing such optical sensing. This aspect of the disclosed optical sensor technology enables a wide range of LCD display screens in smartphones, tablets or other electronic devices with enhanced functions from the optical sensing of the disclosed optical sensor technology.
For example, for an existing phone assembly design that does not provide a separate fingerprint sensor as in certain Apple iPhones or Samsung Galaxy smartphones, such an existing phone assembly design can integrate the under-screen optical fingerprint sensor module as disclosed herein without changing the touch sensing-display screen assembly to provide an added on-screen fingerprint sensing function. Because the disclosed optical sensing does not require a separate designated sensing area or port as in the case of certain Apple iPhones/Samsung Galaxy phones with a front fingerprint sensor outside the display screen area, or some smartphones with a designated rear fingerprint sensor on the backside like in some models by Huawei, Xiaomi, Google or Lenovo, the integration of the on-screen fingerprint sensing disclosed herein does not require a substantial change to the existing phone assembly design or the touch sensing display module that has both the touch sensing layers and the display layers. Based on the disclosed optical sensing technology in this document, no external sensing port and no extern hardware button are needed on the exterior of a device are needed for adding the disclosed optical fingerprint sensor module for fingerprint sensing. The added optical fingerprint sensor module and the related circuitry are under the display screen inside the phone housing and the fingerprint sensing can be conveniently performed on the same touch sensing surface for the touch screen.
For another example, due to the above described nature of the optical fingerprint sensor module for fingerprint sensing, a smartphone that integrates such an optical fingerprint sensor module can be updated with improved designs, functions and integration mechanism without affecting or burdening the design or manufacturing of the LCD display screens to provide desired flexibility to device manufacturing and improvements/upgrades in product cycles while maintaining the availability of newer versions of optical sensing functions to smartphones, tablets or other electronic devices using LCD display screens. Specifically, the touch sensing layers or the LCD display layers may be updated in the next product release without adding any significant hardware change for the fingerprint sensing feature using the disclosed under-screen optical fingerprint sensor module. Also, improved on-screen optical sensing for fingerprint sensing or other optical sensing functions by such an optical fingerprint sensor module can be added to a new product release by using a new version of the under-screen optical fingerprint sensor module without requiring significant changes to the phone assembly designs, including adding additional optical sensing functions.
The above and other features of the disclosed optical sensor technology can be implemented to provide a new generation of electronic devices with improved fingerprint sensing and other sensing functions, especially for smartphones, tablets and other electronic devices with LCD display screens to provide various touch sensing operations and functions and to enhance the user experience in such devices. The features for optical fingerprint sensor modules disclosed herein may be applicable to various display panels based on different technologies including both LCD and OLED displays. The specific examples below are directed to LCD display panels and optical fingerprint sensor modules placed under LCD display panels.
In implementations of the disclosed technical features, additional sensing functions or sensing modules, such as a biomedical sensor, e.g., a heartbeat sensor in wearable devices like wrist band devices or watches, may be provided. In general, different sensors can be provided in electronic devices or systems to achieve different sensing operations and functions.
The disclosed technology can be implemented to provide devices, systems, and techniques that perform optical sensing of human fingerprints and authentication for authenticating an access attempt to a locked computer-controlled device such as a mobile device or a computer-controlled system, that is equipped with a fingerprint detection module. The disclosed technology can be used for securing access to various electronic devices and systems, including portable or mobile computing devices such as laptops, tablets, smartphones, and gaming devices, and other electronic devices or systems such as electronic databases, automobiles, bank ATMs, etc.
As described herein, embodiments provide enhancement film implementations for integration into under-display optical sensing modules, including under-screen optical fingerprint modules. For the sake of added clarity and context, examples are described of various designs for an under-screen optical fingerprint sensor module for collecting an optical signal to the optical detectors and providing desired optical imaging such as a sufficient imaging resolution. These and other embodiments of under-display optical fingerprint sensing implementations are further described in the following patent documents, which are hereby incorporated by reference in their entirety: U.S. patent application Ser. No. 15/616,856; U.S. patent application Ser. No. 15/421,249; U.S. patent application Ser. No. 16/190,138; U.S. patent application Ser. No. 16/190,141; U.S. patent application Ser. No. 16/246,549; and U.S. patent application Ser. No. 16/427,269.
As a specific example,
In implementations, the top surface of the device screen assembly can be a surface of an optically transparent layer serving as a user touch sensing surface to provide multiple functions, such as (1) a display output surface through which the light carrying the display images passes through to reach a viewer's eyes, (2) a touch sensing interface to receive a user's touches for the touch sensing operations by the touch sensing screen module, and (3) an optical interface for on-screen fingerprint sensing (and possibly one or more other optical sensing functions). This optically transparent layer can be a rigid layer such as a glass or crystal layer or a flexible layer.
One example of a display screen is an LCD display having LCD layers and a thin film transistor (TFT) structure or substrate. A LCD display panel is a multi-layer liquid crystal display (LCD) module that includes LCD display backlighting light sources (e.g., LED lights) emitting LCD illumination light for LCD pixels, a light waveguide layer to guide the backlighting light, and LCD structure layers which can include, e.g., a layer of liquid crystal (LC) cells, LCD electrodes, transparent conductive ITO layer, an optical polarizer layer, a color filter layer, and a touch sensing layer. The LCD module also includes a backlighting diffuser underneath the LCD structure layers and above the light waveguide layer to spatially spread the backlighting light for illuminating the LCD display pixels, and an optical reflector film layer underneath the light waveguide layer to recycle backlighting light towards the LCD structure layers for improved light use efficiency and the display brightness. For optical sensing, one or more separate illumination light sources are provided and are operated independently from the backlighting light sources of the LCD display module.
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This device and other devices disclosed herein can be further configured to include various features. For example, a device electronic control module can be included in the device to grant a user's access to the device if a detected fingerprint matches a fingerprint an authorized user. In addition, the optical fingerprint sensor module is configured to, in addition to detecting fingerprints, also detect a biometric parameter different form a fingerprint by optical sensing to indicate whether a touch at the top transparent layer associated with a detected fingerprint is from a live person, and the device electronic control module is configured to grant a user's access to the device if both (1) a detected fingerprint matches a fingerprint an authorized user and (2) the detected biometric parameter indicates the detected fingerprint is from a live person. The biometric parameter can include, e.g., whether the finger contains a blood flow, or a heartbeat of a person.
For example, the device can include a device electronic control module coupled to the display panel structure to supply power to the light emitting display pixels and to control image display by the display panel structure, and, in a fingerprint sensing operation, the device electronic control module operates to turn off the light emitting display pixels in one frame to and turn on the light emitting display pixels in a next frame to allow the optical sensor array to capture two fingerprint images with and without the illumination by the light emitting display pixels to reduce background light in fingerprint sensing.
For another example, a device electronic control module may be coupled to the display panel structure to supply power to the LCD display panel and to turn off power to the backlighting of the LCD display panel in a sleep mode, and the device electronic control module may be configured to wake up the display panel structure from the sleep mode when the optical fingerprint sensor module detects the presence of a person's skin at the designated fingerprint sensing region of the top transparent layer. More specifically, in some implementations, the device electronic control module can be configured to operate one or more illumination light sources in the optical fingerprint sensor module to intermittently emit light, while turning off power to the LCD display panel (in the sleep mode), to direct the intermittently emitted illumination light to the designated fingerprint sensing region of the top transparent layer for monitoring whether there is a person's skin in contact with the designated fingerprint sensing region for waking up the device from the sleep mode.
For another example, the device can include a device electronic control module coupled to the optical fingerprint sensor module to receive information on multiple detected fingerprints obtained from sensing a touch of a finger and the device electronic control module is operated to measure a change in the multiple detected fingerprints and determines a touch force that causes the measured change. For instance, the change may include a change in the fingerprint image due to the touch force, a change in the touch area due to the touch force, or a change in spacing of fingerprint ridges.
For another example, the top transparent layer can include a designated fingerprint sensing region for a user to touch with a finger for fingerprint sensing and the optical fingerprint sensor module below the display panel structure can include a transparent block in contact with the display panel substrate to receive light that is emitted from the display panel structure and returned from the top transparent layer, an optical sensor array that receives the light and an optical imaging module that images the received light in the transparent block onto the optical sensor array. The optical fingerprint sensor module can be positioned relative to the designated fingerprint sensing region and structured to selectively receive returned light via total internal reflection at the top surface of the top transparent layer when in contact with a person's skin while not receiving the returned light from the designated fingerprint sensing region in absence of a contact by a person's skin.
For yet another example, the optical fingerprint sensor module can be structured to include an optical wedge located below the display panel structure to modify a total reflection condition on a bottom surface of the display panel structure that interfaces with the optical wedge to permit extraction of light out of the display panel structure through the bottom surface, an optical sensor array that receives the light from the optical wedge extracted from the display panel structure, and an optical imaging module located between the optical wedge and the optical sensor array to image the light from the optical wedge onto the optical sensor array.
The optical fingerprint sensor module 702 in this particular implementation example is placed under LCD display module 433. One or more illumination light sources, e.g., an illumination light source 436 under the LCD display module 433 or/and another one or more illumination light sources located under the top cover glass 431, are provided for providing the illumination light or probe light for the optical sensing by the optical fingerprint sensor module 702 and can be controlled to emit light to at least partially pass through the LCD display module 433 to illuminate the fingerprint sensing zone 615 on the top transparent layer 431 within the device screen area for a user to place a finger therein for fingerprint identification. The illumination light from the one or more illumination light sources 436 can be directed to the fingerprint sensing area 615 on the top surface as if such illumination light is from a fingerprint illumination light zone 613. Another one or more illumination light sources may be located under the top cover glass 431 and may be placed adjacent to the fingerprint sensing area 615 on the top surface to direct produced illumination light to reach the top cover glass 433 without passing through the LCD display module 433. In some designs, one or more illumination light sources may be located above the bottom surface of the top cover glass 431 to direct produced illumination light to reach the fingerprint sensing region above the top surface of the top cover glass 433 without necessarily passing through the top cover glass 431, e.g., directing illuminating the finger above the top cover glass 431.
As illustrated in
In this design of using one or more illumination light sources 436 to provide the illumination light for optical fingerprint sensing, each illumination light source 436 maybe controlled in some implementations to turn on intermittently with a relatively low cycle to reduce the power used for the optical sensing operations. The fingerprint sensing operation can be implemented in a two-step process in some implementations: first, the one or more illumination light sources 436 are turned on in a flashing mode without turning on the LCD display panel to use the flashing light to sense whether a finger touches the sensing zone 615 and, once a touch in the zone 615 is detected, the optical sensing module is operated to perform the fingerprint sensing based on optical sensing and the LCD display panel may be turned on.
In the example in
In this particular example, the optical light path design is structured so that the illumination light enters the cover top surface within the total reflection angles on the top surface between the substrate and air interface and, therefore, the reflected light is collected most effectively by the imaging optics and imaging sensor array in the block 702. In this design, the image of the fingerprint ridge/valley area exhibits a maximum contrast due to the total internal reflection condition at each finger valley location where the finger tissue does not touch the top cover surface of the top cover glass 431. Some implementations of such an imaging system may have undesired optical distortions that would adversely affect the fingerprint sensing. Accordingly, the acquired image may be further corrected by a distortion correction during the imaging reconstruction in processing the output signals of the optical sensor array in the block 702 based on the optical distortion profile along the light paths of the returned light at the optical sensor array. The distortion correction coefficients can be generated by images captured at each photodetector pixel by scanning a test image pattern one line pixel at a time, through the whole sensing area in both X direction lines and Y direction lines. This correction process can also use images from tuning each individual pixel on one at a time, and scanning through the whole image area of the photodetector array. This correction coefficients only need to be generated one time after assembly of the sensor.
The background light from environment (e.g., sunlight or room illumination light) may enter the image sensor through the LCD panel top surface, and through holes in the LCD display assembly 433. Such background light can create a background baseline in the interested images from a finger and thus may undesirably degrade the contrast of a captured image. Different methods can be used to reduce this undesired baseline intensity caused by the background light. One example is to tune on and off the illumination light source 436 at a certain illumination modulation frequency f and the image sensor accordingly acquires the received images at the same illumination modulation frequency by phase synchronizing the light source driving pulse and image sensor frame. Under this operation, only one of the image phases contain light from the light source. In implementing this technique, the imaging capturing can be timed to capture images with the illumination light on at even (or odd) frames while turning off the illumination light at odd (or even) frames and, accordingly, subtracting even and odd frames can be used to obtain an image which is mostly formed by light emitted from the modulated illumination light source with significantly reduced background light. Based on this design, each display scan frame generates a frame of fingerprint signals and two sequential frames of signals are obtained by turning on the illumination light in one frame and off in the other frame. The subtraction of adjacent frames can be used to minimize or substantially reduce the ambient background light influence. In implementations, the fingerprint sensing frame rate can be one half of the display frame rate.
In the example shown in
The one or more illumination light sources 436 in
The one or more illumination light sources 436 can be controlled by the same electronics 704 (e.g., MCU) for controlling the image sensor array in the block 702. The one or more illumination light sources 436 can be pulsed for a short time (e.g., at a low duty cycle) to emit light intermittently and to provide pulse light for image sensing. The image sensor array can be operated to monitor the light pattern at the same pulse duty cycle. If there is a human finger touching the sensing area 615 on the screen, the image that is captured at the imaging sensing array in the block 702 can be used to detect the touching event. The control electronics or MCU 704 connected to the image sensor array in the block 702 can be operated to determine if the touch is by a human finger touch. If it is confirmed that it is a human finger touch event, the MCU 704 can be operated to wake up the smartphone system, turn on the one or more illumination light sources 436 for performing the optical fingerprint sensing), and use the normal mode to acquire a full fingerprint image. The image sensor array in the block 702 sends the acquired fingerprint image to the smartphone main processor 705 which can be operated to match the captured fingerprint image to the registered fingerprint database. If there is a match, the smartphone unlocks the phone to allow a user to access the phone and start the normal operation. If the captured image is not matched, the smartphone produces a feedback to user that the authentication is failed and maintains the locking status of the phone. The user may try to go through the fingerprint sensing again, or may input a passcode as an alternative way to unlock the phone.
In the example illustrated in
In the optical sensing by the under-screen optical fingerprint sensor module in
In the example in
The beam 82 at the finger skin valley location 63 is reflected by the cover glass surface. In some designs, for example, the reflection may be about 3.5% as the reflected light 185 towards bottom layers 524, and the finger valley surface may reflect about 3.3% of the incident light power (light 187) to bottom layers 524 so that the total reflection may be about 6.8%. The majority light 189 is transmitted into the finger tissues 60. Part of the light power in the transmitted light 189 in the figure tissue is scattered by the tissue to contribute to the scattered light 191 towards and into the bottom layers 524.
Therefore, in the example in
For the central light beams 82, the cover glass surface in some designs may reflect about 0.1%-3.5% to light beam 185 that is transmitted into bottom layers 524, the finger skin may reflect about 0.1%-3.3% to light beam 187 that is also transmitted into bottom layers 524. The reflection difference is dependent on whether the light beams 82 meet with finger skin ridge 61 or valley 63. The rest light beam 189 is coupled into the finger tissues 60.
For high contrast light beams 201 and 202 meeting the local totally internal reflection condition, the cover glass surface reflects nearly 100% to light beams 205 and 206 respectively if nothing touches the cover glass surface. When the finger skin ridges touch the cover glass surface and at light beams 201 and 202 positions, most of the light power may be coupled into the finger tissues 60 by light beams 203 and 204.
For high contrast light beams 211 and 212 meeting the local totally internal reflection condition, the cover glass surface reflects nearly 100% to light beams 213 and 214 respectively if nothing touches the cover glass surface. When the finger touches the cover glass surface and the finger skin valleys happen to be at light beams 211 and 212 positions, no light power is coupled into finger tissues 60.
As illustrated in
The disclosed under-screen optical sensing technology can be in various configurations to optically capture fingerprints based on the design illustrated in
Similar to the assumptions in
In this design, the micro lens 621 and the photodiode array 623 define a viewing angle θ for capturing the image of a contact finger in the sensing zone 615. This viewing angle can be aligned properly by controlling the physical parameters or configurations in order to detect a desired part of the cover glass surface in the sensing zone 615. For example, the viewing angle may be aligned to detect the total inner reflection of the LCD display assembly. Specifically, the viewing angle θ is aligned to sense the effective sensing zone 615 on the cover glass surface. The effective sensing cover glass surface 615 may be viewed as a mirror so that the photodetector array effectively detects an image of the fingerprint illumination light zone 613 in the LCD display that is projected by the sensing cover glass surface 615 onto the photodetector array. The photodiode/photodetector array 623 can receive the image of the zone 613 that is reflected by the sensing cover glass surface 615. When a finger touches the sensing zone 615, some of the light can be coupled into the fingerprint's ridges and this will cause the photodetector array to receive light from the location of the ridges to appear as a darker image of the fingerprint. Because the geometrics of the optical detection path are known, the fingerprint image distortion caused in the optical path in the optical fingerprint sensor module can be corrected.
Consider, as a specific example, that the distance H in
If nc is greater than ns, ϕ1 is greater than ϕ2. Thus, the refraction enlarges the sensing width Wc. For example, assuming the finger skin's equivalent RI is about 1.44 at 550 nm and the cover glass index RI is about 1.51, the total reflection incident angle is estimated to be about 41.8° if nothing touches the cover glass top surface, and the total reflection angle is about 73.7° if the finger skin touches the cover glass top surface. The corresponding total reflection angle difference is about 31.9°. If the spacer 618 is made of same material of the cover glass, and the distance from the detection module center to the cover glass top surface is 2 mm, if detection angle width is θ=31.9°, the effective sensing area width Wc is about 5 mm. The corresponding central axis's local incident angle is ϕ1=ϕ2=57.75°. If the material for the special spacer 618 has a refractive index ns about 1.4, and Hs is 1.2 mm and the detection module is tilted at ϕ1=70°. The effective sensing area width is increased to be greater than 6.5 mm. Under those parameters, the detection angle width in the cover glass is reduced to 19°. Therefore, the imaging system for the optical fingerprint sensor module can be designed to desirably enlarge the size of the sensing area 615 on the top transparent layer 431.
the refractive index RI of the special spacer 618 is designed to be sufficiently low (e.g., to use MgF2, CaF2, or even air to form the spacer), the width Wc of the effective sensing area 615 is no longer limited by the thickness of the cover glass 431 and the display module 433. This property provides desired design flexibility. In principle, if the detection module has a sufficient resolution, the effective sensing area may even be increased to cover the entire display screen.
Since the disclosed optical sensor technology can be used to provide a large sensing area for capturing a pattern, the disclosed under-screen optical fingerprint sensor modules may be used to capture and detect not only a pattern of a finger but a larger size patter such a person's palm that is associated with a person for user authentication.
If the light is totally reflected at the sensing surface of the cover glass 431, the reflectance is 100%, of the highest efficiency. However, the light will also be totally reflected at the LCD bottom surface 433b if it is parallel to the cover glass surfaces. The wedge coupler 628 is used to modify the local surface angle so that the light can be coupled out for the detection at the optical sensor array 623. The micro holes in the LCD display module 433 provide the desired light propagation path for light to transmit through the LCD display module 433 for the under-screen optical sensing. The actual light transmission efficiency may gradually be reduced if the light transmission angle becomes too large or when the TFT layer becomes too thick. When the angle is close to the total reflection angle, namely about 41.8° when the cover glass refractive index is 1.5, the fingerprint image looks good. Accordingly, the wedge angle of the wedge coupler 628 may be adjusted to be of a couple of degrees so that the detection efficiency can be increased or optimized. If the cover glass' refractive index is selected to be higher, the total reflection angle becomes smaller. For example, if the cover glass is made of Sapphire which refractive index is about 1.76, the total reflection angle is about 34.62°. The detection light transmission efficiency in the display is also improved. Therefore, this design of using a thin wedge to set the detection angle to be higher than the total reflection angle, and/or to use high refractive index cover glass material to improve the detection efficiency.
In some under-screen optical fingerprint sensor module designs (e.g., those illustrated in
In the above designs where the lens 621 is used, the lens 621 can be designed to have an effective aperture that is larger than the aperture of the holes in the LCD display layers that allow transmission of light through the LCD display module for optical fingerprint sensing. This design can reduce the undesired influence of the wiring structures and other scattering objects in the LCD display module.
The undesired background light in the fingerprint sensing may also be reduced by providing proper optical filtering in the light path. One or more optical filters may be used to reject the environment light wavelengths, such as near IR and partial of the red light etc. In some implementation, such optical filter coatings may be made on the surfaces of the optical parts, including the display bottom surface, prism surfaces, sensor surface etc. For example, human fingers absorb most of the energy of the wavelengths under ˜580 nm, if one or more optical filters or optical filtering coatings can be designed to reject light in wavelengths from 580 nm to infrared, undesired contributions to the optical detection in fingerprint sensing from the environment light may be greatly reduced.
The same optical sensors used for capturing the fingerprint of a user can be used also to capture the scattered light from the illuminated finger as shown by the back scattered light 191 in
The above fingerprint sensor may be hacked by malicious individuals who can obtain the authorized user's fingerprint, and copy the stolen fingerprint pattern on a carrier object that resembles a human finger. Such unauthorized fingerprint patterns may be used on the fingerprint sensor to unlock the targeted device. Hence, a fingerprint pattern, although a unique biometric identifier, may not be by itself a completely reliable or secure identification. The under-screen optical fingerprint sensor module can also be used to as an optical anti-spoofing sensor for sensing whether an input object with fingerprint patterns is a finger from a living person and for determining whether a fingerprint input is a fingerprint spoofing attack. This optical anti-spoofing sensing function can be provided without using a separate optical sensor. The optical anti-spoofing can provide high-speed responses without compromising the overall response speed of the fingerprint sensing operation.
When a nonliving material touches the top cover glass above the fingerprint sensor module, the received signal reveals strength levels that are correlated to the surface pattern of the nonliving material and the received signal does not contain signal components associated with a finger of a living person. However, when a finger of a living person touches the top cover glass, the received signal reveals signal characteristics associated with a living person, including obviously different strength levels because the extinction ratios are different for different wavelengths. This method does not take long time to determine whether the touching material is a part of a living person. In
This optical sensing of different optical absorption behaviors of the blood at different optical wavelengths can be performed in a short period for live finger detection and can be faster than optical detection of a person's heart beat using the same optical sensor.
In LCD displays, the LCD backlighting illumination light is white light and thus contains light at both the visible and IR spectral ranges for performing the above live finger detection at the optical fingerprint sensor module. The LCD color filters in the LCD display module can be used to allow the optical fingerprint sensor module to obtain measurements in
For yet another example, the disclosed optical sensor technology can be used to detect whether the captured or detected pattern of a fingerprint or palm is from a live person's hand by a “live finger” detection mechanism by other mechanisms other than the above described different optical absorptions of blood at different optical wavelengths. For example, a live person's finger tends to be moving or stretching due to the person's natural movement or motion (either intended or unintended) or pulsing when the blood flows through the person's body in connection with the heartbeat. In one implementation, the optical fingerprint sensor module can detect a change in the returned light from a finger or palm due to the heartbeat/blood flow change and thus to detect whether there is a live heartbeat in the object presented as a finger or palm. The user authentication can be based on the combination of the both the optical sensing of the fingerprint/palm pattern and the positive determination of the presence of a live person to enhance the access control. For yet another example, as a person touches the LCD display screen, a change in the touching force can be reflected in one or more ways, including fingerprint pattern deforming, a change in the contacting area between the finger and the screen surface, fingerprint ridge widening, or a change in the blood flow dynamics. Those and other changes can be measured by optical sensing based on the disclosed optical sensor technology and can be used to calculate the touch force. This touch force sensing can be used to add more functions to the optical fingerprint sensor module beyond the fingerprint sensing.
In the above examples where the fingerprint pattern is captured on the optical sensor array via an imaging module, as in
In light of the disclosure in this patent document, various implementations can be made for the optical fingerprint sensor module as disclosed. For example, a display panel can be constructed in which each pixel emitting lights, and can be controlled individually; the display panel includes an at least partially transparent substrate; and a cover substrate, which is substantially transparent. An optical fingerprint sensor module is placed under the display panel to sense the images form on the top of the display panel surface. The optical fingerprint sensor module can be used to sense the images form from light emitting from display panel pixels. The optical fingerprint sensor module can include a transparent block with refractive index lower than the display panel substrate, and an imaging sensor block with an imaging sensor array and an optical imaging lens. In some implementations, the low refractive index block has refractive index in the range of 1.35 to 1.46 or 1 to 1.35.
For another example, a method can be provided for fingerprint sensing, where light emitting from a display panel is reflected off the cover substrate, a finger placed on top of the cover substrate interacts with the light to modulate the light reflection pattern by the fingerprint. An imaging sensing module under the display panel is used to sense the reflected light pattern image and reconstruct fingerprint image. In one implementation, the emitting light from the display panel is modulated in time domain, and the imaging sensor is synchronized with the modulation of the emitting pixels, where a demodulation process will reject most of the background light (light not from pixels being targeted).
As described above, display screens of portable electronic devices are often implemented as an assembly of multiple layers. For example, display screens implemented as touchscreens can include display layers for outputting video data, capacitive touchscreen layers for detecting touch events, a hard top layer, etc. Additional layers are used to integrate under-display optical sensing capabilities, such as fingerprint sensing. For light to reach the sensing components, the light passes through the various layers between the top surface and the sensors (e.g., the photodetectors). To that end, the layers are designed to permit transmission of light, and some layers can be designed to enhance, bend, focus, collimate, reflect, and/or otherwise influence transmission of light through the layers.
The display module 1710 of
One or more other layers of the display module 1710 form a liquid crystal module (LCM) 1720. Below the LCM 1720, the display module 1710 includes an enhancement layer 1725. As described herein, the enhancement layer 1725 can include one or more layers of brightness-enhancement film, such as enhancement films including trapezoidal prism structures. The display module 1710 can further include some or all of a light diffuser 1730, a light guide plate 1735, a reflector film 1740, and a frame 1745. Some embodiments include additional components, such as one or more display light sources 1750, and one or more external light sources 1760 (e.g., for fingerprint and/or other optical sensing).
Implementations of the display light sources 1750 can include LCD display backlighting light sources (e.g., LED lights) that provide white backlighting for the display module 1710. Implementations of the light guide plate 1735 include a waveguide optically coupled with the display light sources 1750 to receive and guide the backlighting light. Implementations of the LCM 1720 include some or all of a layer of liquid crystal (LC) cells, LCD electrodes, a transparent conductive ITO layer, an optical polarizer layer, a color filter layer, a touch sensing layer, etc. Implementations of the light diffuser 1730 include a backlighting diffuser placed underneath the LCM 1720 and above the light guide plate 1735 to spatially spread the backlighting light for illuminating the LCD display pixels in the LCM 1720. Implementations of the reflector film 1740 are placed underneath the light guide plate 1735 to recycle backlighting light towards the LCM 1720 for improved light use efficiency and display brightness.
When the LCD cells in (e.g., in the sensing region 615) are turned on, the LCM 1720 (e.g., the LC cells, electrodes, transparent ITO, polarizer, color filter, touch sensing layer, etc.) can become partially transparent, although the micro structure may interfere and/or block some probe light energy. Embodiments of the light diffuser 1730, the light guide plate 1735, the reflector film 1740, and the frame 1745 are treated to hold the fingerprint sensor and provide a transparent or partially transparent sensing light path, so that a portion of the reflected light from the top surface of the cover layer 1715 can reach sensing elements (e.g., a photo detector array) of the under-display optical sensor. The under-display optical sensor can include any suitable components, such as fingerprint sensor parts, a photodetector array, an optical collimator array for collimating and directing reflected probe light to the photo detector array, and an optical sensor circuit to receive and condition detector output signals from the photo detector array. Embodiments of the photodetector array include a CMOS sensor of CMOS sensing pixels, a CCD sensor array, or any other suitable optical sensor array.
Embodiments of the enhancement layer 1725 include one or more enhancement films. Some conventional enhancement film designs include a prism film with sharp prism ridge and sharp prism valley profile (i.e., a sharp transition at each ridge, and a sharp transition at each valley). When light passes through such a conventional sharp prism structure, the light is bent in different directions, and the imaging tends to be blurred. For example,
As illustrated, each enhancement film layer 1820 is formed with a series of sharp prism structures. Each sharp prism structure includes a sharp ridge 1822 and a sharp valley 1824. The zoomed-in view 1810 of
Embodiments described herein mitigate such blurring by designing the enhancement film to provide vertical viewing windows. For example, the enhancement film is designed with trapezoidal prism structures, for which some or all of the prism structures have a trapezoid ridge and/or a trapezoid valley. A first layer of the enhancement film can be oriented with the trapezoidal features following a first alignment, and a second layer of the enhancement film can be oriented with the trapezoidal features following a second alignment that is orthogonal to the first alignment. In such an arrangement, the orthogonally overlapped enhancement films provide clear viewing windows. Embodiments of such an approach are described with reference to
As illustrated, each enhancement film layer 1920 is formed with a series of trapezoidal-ridge prism structures. Each trapezoidal-ridge prism structure includes a flattened ridge 1922 and a sharp valley 1924. The zoomed-in view 1910 of
As illustrated by
As illustrated, each enhancement film layer 2020 is formed with a series of trapezoidal-valley prism structures. Each trapezoidal-valley prism structure includes a sharp ridge 2022 and a flattened valley 2024. The zoomed-in view 2010 of
As illustrated by
As illustrated, each enhancement film layer 2120 is formed with a series of trapezoidal-ridge-trapezoidal-valley prism structures. Each trapezoidal-ridge-trapezoidal-valley prism structure includes a flattened ridge 1922 and a flattened valley 2024. The zoomed-in view 2110 of
As illustrated by
While
Further, flattened regions of the enhancement layer 1725 can be produced in different ways. In some embodiments, the prism structures of the enhancement layer 1725 are initially manufactured in with trapezoidal features. For example, molds, additive manufacturing (e.g., three-dimensional printing), or other techniques are used to manufacture the prism structures to have flattened ridges and/or flattened valleys. In other embodiments, the prism structures of the enhancement layer 1725 are initially manufactured as sharp prism structures, and subsequently refined to form trapezoidal features. For example, the prism structures are initially manufactured with sharp ridges, and the sharp ridges are subsequently ground or polished down to form flattened ridges.
While this disclosure contains many specifics, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this patent document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.
Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments.
Only a few implementations and examples are described and other implementations, enhancements and variations can be made based on what is described and illustrated in this patent document.
A recitation of “a”, “an” or “the” is intended to mean “one or more” unless specifically indicated to the contrary.
Ranges may be expressed herein as from “about” one specified value, and/or to “about” another specified value. The term “about” is used herein to mean approximately, in the region of, roughly, or around. When the term “about” is used in conjunction with a numerical range, it modifies that range by extending the boundaries above and below the numerical values set forth. In general, the term “about” is used herein to modify a numerical value above and below the stated value by a variance of 10%. When such a range is expressed, another embodiment includes from the one specific value and/or to the other specified value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the specified value forms another embodiment. It will be further understood that the endpoints of each of the ranges are included with the range.
All patents, patent applications, publications, and descriptions mentioned here are incorporated by reference in their entirety for all purposes. None is admitted to be prior art.
